Heat/acoustic wave conversion component and heat/acoustic wave conversion unit

ABSTRACT

A heat/acoustic wave conversion component includes a plurality of monolithic honeycomb segments each including a partition wall that defines a plurality of cells extending between both end faces, and the plurality of monolithic honeycomb segments each mutually converts heat exchanged between the partition wall and the working fluid in the cells and energy of acoustic waves resulting from oscillations of the working fluid. In the heat/acoustic wave conversion component including the plurality of honeycomb segments each being monolithic configured, hydraulic diameter HD of the cells is 0.4 mm or less, open frontal area of the honeycomb segments is 60% or more and 93% or less, heat conductivity of the honeycomb segments is 5 W/mK or less, and a ratio HD/L of the hydraulic diameter HD to the length L of the honeycomb segment is 0.005 or more and less than 0.02.

The present application is an application based on JP 2014-192022 filedon Sep. 19, 2014 with Japan Patent Office, the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to heat/acoustic wave conversioncomponents and heat/acoustic wave conversion units. More particularly,the present invention relates to a heat/acoustic wave conversioncomponent to convert heat and acoustic-wave energy mutually, and aheat/acoustic wave conversion unit including a heat/acoustic waveconversion component and a heat exchanger.

Description of the Related Art

Recently society as a whole has been becoming more and more interestedin effective use of energy resources, and so various techniques to reuseenergy have been developed on a trial basis. Among them, an energyrecycling system attracts attention because the acquisition rate (energyefficiency) of the energy acquired is high. The energy recycling systemconverts heat of high-temperature fluid, such as exhaust gas fromautomobiles, to acoustic-wave energy by a thermoacoustic effect, andfinally outputs such energy in the form of electric power. Variousefforts have been made toward the practical use of such a system.

Simply speaking, a thermoacoustic effect is a phenomenon to generateacoustic waves using heat. More specifically, the thermoacoustic effectis a phenomenon to oscillate an acoustic-wave transmitting medium in thethin tube to generate acoustic waves when heat is applied to one endpart of a thin tube to form a temperature gradient at the thin tube.Since it is effective to generate acoustic waves using a large number ofsuch thin tubes at one time, a honeycomb structure including a largenumber of through holes each having a small diameter is often used as acollective form of the thin tubes causing a thermoacoustic effect (seee.g., Patent Documents 1 to 3).

Meanwhile the honeycomb structure itself has been used for variouspurposes, without reference to the thermoacoustic effect, because of itsthree-dimensional geometry having a large surface area. For instance, atypical example is a honeycomb structure to load catalyst for exhaustpurification to remove fine particles from exhaust gas of automobiles,and various types of structures have been developed conventionally.Another example is a honeycomb structure having small through holes of afew tens to a few hundreds μm in diameter, which is developed as an ioncatalyst (see Non-Patent Documents 1, 2, for example). They aremanufactured by a chemical method solely, which is totally differentfrom extrusion that is typically used for honeycomb structures asfilters.

In this way, although honeycomb structures have been well knownconventionally, they are required to have specific properties to besuitable for a thermoacoustic effect when these structures are used asheat/acoustic wave conversion components to exert the thermoacousticeffect. For example, in order to exert a high thermoacoustic effect, thethrough holes preferably have a small diameter, and Patent Document 3proposes a honeycomb structure for a thermoacoustic effect, includingthrough holes having a diameter of 0.5 mm or more and less 1.0 mm thatis smaller than that of honeycomb structures to load catalyst forexhaust purification. Although the honeycomb structures in Non-PatentDocuments 1 and 2 have a very small pore diameter, they are manufacturedby a chemical method solely, and so they have limited lengths anddurability and so are not suitable for the honeycomb structure for athermoacoustic effect very much. On the other hand, the honeycombstructure for a thermoacoustic effect of Patent Document 3 satisfies anecessary condition that is durable in the use as a heat/acoustic waveconversion component to exert a thermoacoustic effect, and then has theadvantage of having an excellent heat/acoustic wave conversion function.

-   [Patent Document 1] JP-A-2005-180294-   [Patent Document 2] JP-A-2012-112621-   [Patent Document 3] JP-A-2012-237295-   [Non-Patent Document 1]    URL:http://www.mesl.t.u-tokyo.ac.jp/ja/research/tpv.html on the    Internet-   [Non-Patent Document 2]    URL:http://www.ricoh.com/ja/technology/tech/009_honeycomb.html on    the Internet

SUMMARY OF THE INVENTION

Patent Document 3, however, does not consider the durability of thecomponent at all when it is used for a long time as a heat/acoustic waveconversion component. For instance, when the component is used for along time as a heat/acoustic wave conversion component, then localheating and local cooling will be performed continuously to let thecomponent have a temperature gradient, and so the component has to havesufficient durability against thermal stress resulting from such atemperature difference. In this way, honeycomb structures, when they areused as a heat/acoustic wave conversion component, have to be improvedmore.

In view of the above-mentioned circumstances, the present invention aimsto provide a heat/acoustic wave conversion component having a honeycombstructure and with improved durability, and a heat/acoustic waveconversion unit including such a heat/acoustic wave conversion componentand a heat exchanger.

To fulfill the above-mentioned object, the present invention providesthe following heat/acoustic wave conversion component and heat/acousticwave conversion unit.

[1] A heat/acoustic wave conversion component having a first end faceand a second end face, includes: a plurality of monolithic honeycombsegments each including a partition wall that defines a plurality ofcells extending from the first end face to the second end face, insideof the cells being filled with working fluid that oscillates to transmitacoustic waves, the plurality of monolithic honeycomb segments eachmutually converting heat exchanged between the partition wall and theworking fluid and energy of acoustic waves resulting from oscillationsof the working fluid; a bonding part that mutually bonds side faces ofthe plurality of honeycomb segments; and a circumferential wall thatsurrounds a circumferential face of a honeycomb structure body made upof the plurality of honeycomb segments and the bonding part. Hydraulicdiameter HD of the heat/acoustic wave conversion component is 0.4 mm orless, where the hydraulic diameter HD is defined as HD=4×S/C, where Sdenotes an area of a cross-section of each cell perpendicular to thecell extending direction and C denotes a perimeter of the cross section,an open frontal area at each end face of the honeycomb segments is 60%or more and 93% or less, heat conductivity of a material making up thehoneycomb segments is 5 W/mK or less, and let that L denotes a length ofeach honeycomb segment from the first end face to the second face, aratio HD/L of the hydraulic diameter HD to the length L of the honeycombsegment is 0.005 or more and less than 0.02.

[2] In the heat/acoustic wave conversion component according to [1], thecells have the cross section of a triangular shape, and a cross sectionof the honeycomb segments that is parallel to the cross section of thecells has a hexagonal shape.

[3] In the heat/acoustic wave conversion component according to [1], thecells have the cross section of a triangular shape, and a cross sectionof the honeycomb segments that is parallel to the cross section of thecells has a triangular shape.

[4] In the heat/acoustic wave conversion component according to any oneof [1] to [3], Young's modulus of materials making up the bonding partand the circumferential wall are both less than 30% of Young's modulusof a material making up the honeycomb segments, a thermal expansioncoefficient of the material making up the bonding part is 70% or moreand less than 130% of a thermal expansion coefficient of the materialmaking up the honeycomb segments, and heat capacity per unit volume ofthe material making up the bonding part is 50% or more of heat capacityper unit volume of the material making up the honeycomb segments.

[5] In the heat/acoustic wave conversion component according to any oneof [1] to [4], a bonding width of two of the honeycomb segments bondedmutually is 0.2 mm or more and 4 mm or less, and in a planeperpendicular to the extending direction, a ratio of a totalcross-sectional area of the bonding part to a cross-sectional area ofthe heat/acoustic wave conversion component is 10% or less.

[6] In the heat/acoustic wave conversion component according to any oneof [1] to [5], each of the plurality of honeycomb segments has across-sectional area in a plane perpendicular to the extending directionthat is 3 cm² or more and 12 cm² or less.

[7] In the heat/acoustic wave conversion component according to any oneof [1] to [6], let that D denotes an equivalent circle diameter of across section of the heat/acoustic wave conversion component in a planeperpendicular to the extending direction, the equivalent circle diameterD is 30 mm or more and 100 mm or less, and a ratio L/D of the length Lof the honeycomb segments to the equivalent circle diameter D is 0.3 ormore and 1.0 or less.

[8] In the heat/acoustic wave conversion component according to any oneof [1] to [7], the material making up the honeycomb segments has a ratioof thermal expansion at 20 to 800° C. that is 6 ppm/K or less.

[9] In the heat/acoustic wave conversion component according to any oneof [1] to [8], the honeycomb segments have a length L that is 5 mm ormore and 60 mm or less.

[10] A heat/acoustic wave conversion unit includes the heat/acousticwave conversion component according to any one of [1] to [9], in a statewhere inside of the plurality of cells of the honeycomb segments isfilled with the working fluid, when there is a temperature differencebetween a first end part on the first end face side and a second endpart on the second end face side, the honeycomb segments oscillating theworking fluid along the extending direction in accordance with thetemperature difference and generating acoustic waves; and a pair of heatexchangers that are disposed in a vicinity of the first end part and thesecond end part of the heat/acoustic wave conversion component,respectively, the heat exchangers exchanging heat with the both endparts to give a temperature difference between the both end parts.

[11] A heat/acoustic wave conversion unit includes: the heat/acousticwave conversion component according to any one of [1] to [9], in a statewhere inside of the plurality of cells of the honeycomb segments isfilled with the working fluid, and when the working fluid oscillatesalong the extending direction while receiving acoustic wavestransmitted, the honeycomb segments generating a temperature differencebetween a first end part on the first end face side and a second endpart on the second end face side in accordance with oscillations of theworking fluid; a heat exchanger that is disposed in a vicinity of one ofthe first end part and the second end part of the heat/acoustic waveconversion component, the heat exchanger supplying heat to the one endpart or absorbing heat from the one end part to keep a temperature atthe one end part constant; and a hot heat/cold heat output unit that isdisposed in a vicinity of the other end part of the first end part andthe second end part of the heat/acoustic wave conversion component thatis on the opposite side of the one end part, the hot heat/cold heatoutput unit outputting hot heat or cold heat obtained from exchanging ofheat with the other end part so that, in a state where the temperatureof the one end part is kept constant by the heat exchanger and when theheat/acoustic wave conversion component receives acoustic wavestransmitted, the other end part has a temperature difference inaccordance with oscillations of the working fluid due to transmission ofthe acoustic waves with reference to the one end part kept at theconstant temperature. Here, “outputting hot heat or cold heat” means,for example, “outputting fluid whose temperature is increased or fluidwhose temperature is decreased”.

Since the heat/acoustic wave conversion unit of the present inventionhas values of hydraulic diameter, open frontal area, heat conductivity,and a ratio HD/L of the hydraulic diameter HD to the length L of thehoneycomb segment that are in the numerical ranges defined in the above[1], the heat/acoustic wave conversion component can achieve improveddurability while keeping sufficient energy conversion efficiency toconvert heat into acoustic wave energy by a thermoacoustic effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows the configuration of a power generationsystem, to which one embodiment of a heat/acoustic wave conversion unitand a heat/acoustic wave conversion component of the present inventionis applied.

FIG. 2 schematically shows a cold heat generation system, to which theheat/acoustic wave conversion unit and the heat/acoustic wave conversioncomponent in FIG. 1 are applied.

FIG. 3 schematically shows the configuration of the heat/acoustic waveconversion unit of FIG. 1.

FIG. 4 is a perspective view showing the appearance of thehigh-temperature side heat exchanger in the heat/acoustic waveconversion unit of FIG. 3.

FIG. 5 is a cross-sectional view of the high-temperature side heatexchanger when viewing an inflow port and an outflow port of thehigh-temperature side annular tube in a plane.

FIG. 6 schematically shows one form of a heat/acoustic wave conversionunit including another honeycomb structure fitted in thehigh-temperature side annular tube.

FIG. 7 is a schematic cross-sectional view of the high-temperature sideheat exchanger taken along the line A-A of FIG. 6.

FIG. 8 schematically shows another form of the heat/acoustic waveconversion unit of the present invention that is different from theheat/acoustic wave conversion units in FIGS. 6 and 7.

FIG. 9 schematically shows still another form of the heat/acoustic waveconversion unit that is different from the heat/acoustic wave conversionunit in FIG. 8.

FIG. 10 is a cross-sectional view of a high-temperature side heatexchanger having a mesh structure.

FIG. 11 is a cross-sectional view of the heat/acoustic wave conversioncomponent of FIG. 3 in a plane perpendicular to the penetratingdirection of the cells of the heat/acoustic wave conversion component.

FIG. 12 shows an example where cells have a triangular shape, andhoneycomb segments have a hexagonal shape.

FIG. 13 is a perspective view showing the appearance of a die that isused to prepare a honeycomb formed body in the present embodiment.

FIG. 14 is a perspective view showing the appearance of the die in FIG.13 that is viewed from the opposite side of FIG. 13.

FIG. 15 is an enlarged plan view showing a part of the surface of thedie in FIG. 13.

FIG. 16 schematically shows a cross section of the die of FIG. 15 takenalong the line A-A′.

FIG. 17 shows an example of the retainer plate configuration.

FIG. 18 shows another example of the retainer plate configuration thatis different from FIG. 17.

FIG. 19 shows still another example of the retainer plate configuration.

FIG. 20 shows a further example of the retainer plate configuration thatis different from FIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes embodiments of the present invention, withreference to the drawings. The present invention is not limited to thefollowing embodiments, and is to be understood to include the followingembodiments, to which modifications and improvements are added as neededbased on the ordinary knowledge of a person skilled in the art withoutdeparting from the scope of the present invention.

FIG. 1 schematically shows the configuration of a power generationsystem, to which one embodiment of a heat/acoustic wave conversion unitand a heat/acoustic wave conversion component of the present inventionis applied.

A power generation system 1000 in FIG. 1 includes a heat/acoustic waveconversion unit 100, a looped tube 4, a resonant tube 5 and an energyconverter 6.

The looped tube 4 is a loop-shaped tube that is connected to an end onthe upper side (upper end) and an end on the lower side (lower end) inthe drawing of the heat/acoustic wave conversion unit 100. The resonanttube 5 is a straight tube, having one end connected to the looped tube 4and the other end connected to the energy converter 6. Herein theresonant tube 5 and the energy converter 6 as a whole makes up a tubethat is substantially closed in the end on the right side of thedrawing.

The heat/acoustic wave conversion unit 100 includes a heat/acoustic waveconversion component 1, a high-temperature side heat exchanger 2 and alow-temperature side heat exchanger 3.

The high-temperature side heat exchanger 2 receives the inflow of heatedfluid at high temperatures (e.g., high-temperature exhaust gas), andtransmits the heat thereof to the lower end of the heat/acoustic waveconversion component 1 of FIG. 1 to let the heated fluid having atemperature lower than that at the time of inflow flow out. On the otherhand, the low-temperature side heat exchanger 3 receives the inflow ofcooled fluid (e.g., water) at relatively low temperatures compared withthe heated fluid flowing in the high-temperature side heat exchanger 2and transmits the cold heat to the upper end of the heat/acoustic waveconversion component 1 of FIG. 1 to let the cooled fluid having atemperature higher than that at the inflow flow out. Such functions ofthe high-temperature side heat exchanger 2 and the low-temperature sideheat exchanger 3 yield the state where the lower end of theheat/acoustic wave conversion component 1 has a relatively highertemperature than at the upper end. The heat/acoustic wave conversioncomponent 1 has a honeycomb structure including a plurality of throughholes (hereinafter called cells) like thin tubes that are elongatedvertically in the drawing. Each cell is partitioned from the neighboringcells by a partition wall, and is in communication with the looped tube4 via the high-temperature side heat exchanger 2 and the low-temperatureside heat exchanger 3.

Herein the looped tube 4, the resonant tube 5 and each cell of theheat/acoustic wave conversion component 1 are internally filled withworking fluid that generates oscillations of longitudinal waves andtransmits acoustic waves. An example of the working fluid includes gashaving low viscosity and being less reactive, such as rare gas.

In such a heat/acoustic wave conversion component 1, when there is atemperature difference as stated above at the both ends, the workingfluid in each cell starts to oscillate in the penetrating direction ofthe cells. Then the oscillations are transmitted as acoustic wavesexternally from the heat/acoustic wave conversion component 1. Such aphenomenon of the working fluid oscillating in response to the giventemperature difference is called self-induced oscillations, and is aconventionally well-known phenomenon that occurs when a temperaturegradient is given to a thin tube. A thermoacoustic effect refers togeneration of acoustic waves due to the self-induced oscillation ofworking fluid resulting from heat. The following briefly describes thisself-induced oscillation (a lot of documents describe the details, andPatent Document 3 also provides the detailed descriptions thereon, forexample).

When giving a temperature gradient to a thin tube, then working fluidinside of the thin tube on the high-temperature side absorbs heat fromthe wall surface of the tube and expands from the high-temperature sideto the low-temperature side. Then, the working fluid releases heat tothe wall surface on the low-temperature side and is compressed, and thenreturns back to the high-temperature side. Such exchange of heat withthe wall surface and expansion/compression are repeated, which resultsin oscillation of the working fluid in the elongation direction of thetube. Simply speaking, such motion of the working fluid can said to bethe motion to convey heat so as to alleviate (weaken) the temperaturegradient at the wall surface. As can be clear from this description aswell, such a phenomenon occurs only when the tube is so thin that thethermal effects from the wall surface are large on the working fluidinside. That is, as the tube is made thicker, the thermal effect fromthe wall surface decreases (i.e., it becomes closer to an adiabaticstate), and so such self-induced oscillation hardly occurs. Then, thethickness of the tube is an important factor to generate acoustic wavesby the self-induced oscillation, and the thickness of the tube can beevaluated more quantitatively based on a hydraulic diameter HD that isdefined as HD=4×S/C, where S denotes the cross-sectional area of thetube and C denotes the perimeter of this section.

Referring back to FIG. 1, the power generation system 1000 is describedbelow again.

Since the heat/acoustic wave conversion component 1 includes a pluralityof cells like thin tubes and the self-induced oscillation occurs in eachcell, acoustic waves as the collection of oscillations of the workingfluid in these plurality of cells are then issued from the heat/acousticwave conversion component 1 to the looped tube 4. Then such acousticwaves are transmitted through the looped tube 4 in the direction of thedotted arrows in the drawing. Most of the acoustic waves transmittedthrough the looped tube 4 travels in the resonant tube 5 to the right inthe drawing. As described above, the resonant tube 5 and the energyconverter 6 as a whole makes up a tube that is substantially closed inthe end on the right side of the drawing, and so some of the acousticwaves are reflected and travel to the left in the opposite direction inthe drawing. Then, both of these traveling waves are overlapped in theresonant tube 5. At this time, if the frequency of the traveling wavesmatches with the resonant frequency that is determined, for example, bythe length of the resonant tube 5 then so-called resonance occurs in theresonant tube 5, and steady waves are generated, which are overlappedwaves of both of these traveling waves and have the resonant frequency.In the drawing, the double-headed arrow in the dashed-dotted lineindicates the presence of the steady waves.

Herein the energy converter 6 is equipped with a mechanism not shownthat is capable of changing the effective length of the resonant tube 5,which can adjust the resonance frequency so as to cause the resonance.An exemplary mechanism to change the effective length of the resonanttube 5 includes one described in Patent Document 1, for example.Although the following describes the case where the effective length ofthe resonant tube 5 can be changed, in the power generation system 1000of FIG. 1, a dominant frequency component of the frequency components ofacoustic waves generated at the heat/acoustic wave conversion component1 and traveling through the looped tube 4 may be determined beforehand,and the length of the resonant tube 5 may be configured beforehand to bea special length which makes the frequency of the dominant frequencycomponent the resonance frequency.

The energy converter 6 is equipped with a mechanism to convert acousticwaves into electrical signals as well. An exemplary conversion mechanismof such a type includes a mechanism equipped with a microphone asdescribed in Patent Document 1. Although the conversion mechanismincluding a microphone is the simplest one, the conversion mechanism isnot limited to such a mechanism including a microphone. For instance,conventionally known various mechanisms (e.g., the mechanism of PatentDocument 2), which is to convert acoustic-wave energy to mechanicalenergy and then convert such mechanical energy to electric power byelectromagnetic induction, can be used.

With the configuration as stated above, the power generation system 1000of FIG. 1 can convert heat of high-temperature heated fluid (e.g.,high-temperature exhaust gas) flowing into the high-temperature sideheat exchanger 2 into electric power, and so enables effective use(recycling) of energy.

Next the following describes a cold heat generation system, to which theheat/acoustic wave conversion unit 100 and the heat/acoustic waveconversion component 1 as stated above are applied.

FIG. 2 schematically shows a cold heat generation system, to which theheat/acoustic wave conversion unit 100 and the heat/acoustic waveconversion component 1 in FIG. 1 are applied.

A cold heat generation system 2000 in FIG. 2 includes a looped tube 4′,a transmission tube 5′, an acoustic-wave generation part 7, and theheat/acoustic wave conversion unit 100 described referring to FIG. 1.

The looped tube 4′ is a loop-shaped tube that is connected to an end onthe upper side (upper end) and an end on the lower side (lower end) ofthe heat/acoustic wave conversion unit 100 in FIG. 2, and is incommunication with the plurality of cells of the heat/acoustic waveconversion component 1 via the high-temperature side heat exchanger 2and the low-temperature side heat exchanger 3. The transmission tube 5′is a straight tube, having one end connected to the looped tube 4′ andthe other end connected to the acoustic-wave generation part 7. Theacoustic-wave generation part 7 has a function of generating acousticwaves, and an example of the acoustic-wave generation part 7 includes aspeaker that receives electric power and outputs acoustic waves. Anotherexample is a system that is obtained by removing the energy converter 6from the power generation system 1000 in FIG. 1 and that receives heatand generates acoustic waves (in this case, the resonant tube 5 on theright side is an open end where no reflections occur, and so unlike thestate of FIG. 1, traveling waves toward right are transmitted in theresonant tube 5).

Although the heat/acoustic wave conversion unit 100 has the sameconfiguration as that described with reference to FIG. 1, it isconfigured so that, unlike FIG. 1, cooled fluid (e.g., water), which issimilar to the cooled fluid flowing into the low-temperature side heatexchanger 3 in FIG. 1, flows into both of the high-temperature side heatexchanger 2 and the low-temperature side heat exchanger 3 of FIG. 2.

Herein the looped tube 4′, the transmission tube 5′ and each cell of theheat/acoustic wave conversion component 1 are internally filled withworking fluid that generates oscillations of longitudinal waves andtransmits acoustic waves. Working fluid similar to that used in thepower generation system 1000 of FIG. 1 can be used.

Acoustic waves generated at the acoustic-wave generation part 7 aretransmitted through the transmission tube 5′ in the direction of thedashed-dotted arrow in FIG. 2, and then are transmitted through thelooped tube 4′ in the direction of the dashed line arrow in FIG. 2.Then, the acoustic waves reach the heat/acoustic wave conversion unit100, and travel in each cell from the upper side in FIG. 2 of theheat/acoustic wave conversion component 1. At this time, due to heattransport by acoustic waves, the system can have a state where the endon the high-temperature side heat exchanger 2 side has a relativelyhigher in temperature than the end on the low-temperature side heatexchanger 3 side. At the high-temperature side heat exchanger 2, cooledfluid close to the ambient temperature flows in, and the fluid at atemperature higher than the ambient temperature flows out. On the otherhand, since heat is transported to the end on the high-temperature sideheat exchanger 2 side due to heat transport by acoustic waves, the endof the heat/acoustic wave conversion component 1 on the low-temperatureside heat exchanger 3 side has a temperature lower than the ambienttemperature. Then at the low-temperature side heat exchanger 3, cooledfluid close to the ambient temperature flows in, and the fluid at atemperature lower than the ambient temperature flows out because heat istaken by the end of the heat/acoustic wave conversion component 1 on thelow-temperature side heat exchanger 3 side. In other words, cold heat isoutput in the form of cold water.

With the configuration as stated above, the cold heat generation system2000 in FIG. 2 can output cold heat using acoustic-wave energy generatedat the acoustic-wave generation part 7. Especially when it includes, asthe acoustic-wave generation part 7, the system corresponding to thepower generation system 1000 of FIG. 1 other than the energy converter6, high-temperature heated fluid (e.g., high-temperature exhaust gas)flowing into the high-temperature side heat exchanger 2 of FIG. 1 can beconverted into cold heat, which then enables effective use (recycling)of energy.

As stated above, in the power generation system 1000 in FIG. 1 and thecold heat generation system 2000 in FIG. 2, the heat/acoustic waveconversion unit 100 that is one embodiment of the present inventionplays a very important role. Then the following describes theheat/acoustic wave conversion unit 100 in more details, by way of anexemplary situation where that is used in the power generation system1000 of FIG. 1. The following describes the power generation system 1000of FIG. 1, by way of an example where high-temperature heated fluid(e.g., exhaust gas itself) at about 400 to 600° C. that are typicaltemperatures of the exhaust gas from automobiles flows in thehigh-temperature side heat exchanger 2 of FIG. 1, and low-temperaturecooled fluid (e.g., water) at about 20 to 70° C. flows into thelow-temperature side heat exchanger 3. In this case, a temperaturedifference between both ends of the heat/acoustic wave conversioncomponent 1 is about 330 to 580° C.

Naturally the properties of the heat/acoustic wave conversion unit 100described below are the same as in the case where it is used in the coldheat generation system 2000 of FIG. 2 as well.

FIG. 3 schematically shows the configuration of the heat/acoustic waveconversion unit 100 of FIG. 1.

The heat/acoustic wave conversion unit 100 includes a heat/acoustic waveconversion component 1, a high-temperature side heat exchanger 2 and alow-temperature side heat exchanger 3 as well as a metal member 32 andan interference member 1 a. These components as a whole are stored in ahousing 100 a and are connected to a looped tube 4 (see FIG. 1 also).

The heat/acoustic wave conversion component 1 has a honeycomb structurein which a plurality of cells 14, each being a thin-tube like throughhole, are partitioned and defined by a partition wall 11. Herein, theword “cell” in the present specification refers to a through hole onlythat does not include the partition wall. The heat/acoustic waveconversion component 1 actually has a structure including severalhoneycomb segments having such a honeycomb structure that are bonded,and such a segmented structure will be described later. FIG. 3 shows thearrangement of the cells 14 only, for the ease of explanation. Each cell14 has a penetrating direction (an extending direction in which eachcell 14 extends) that is the vertical direction of FIG. 3, and is openat both end faces of an end face on the low-temperature side heatexchanger 3 side and an end face of the high-temperature side heatexchanger 2 side. The end face of the heat/acoustic wave conversioncomponent 1 on the low-temperature side heat exchanger 3 side is incontact with the metal member 32, and is opposed to the low-temperatureside heat exchanger 3 with the metal member 32 disposed therebetween.Although the metal member 32 is disposed in this case, the presentinvention may have a form without the metal member 32. When the metalmember 32 is omitted, working fluid in contact with a mesh laminationbody 30 described later is cooled, and then the cooled working fluidcomes into contact with the vicinity of the end face of theheat/acoustic wave conversion component 1 due to the displacement of theworking fluid, which corresponds to oscillations of acoustic waves, andcools the vicinity of the end face. When the metal member 32 is omitted,a gap between the heat/acoustic wave conversion component 1 and thelow-temperature side heat exchanger 3 is as small as possiblepreferably.

The metal member 32 is a metal member having a plate shape, at a centerpart of which a plurality of parallel slits (not shown) are formed, andFIG. 3 shows only a side-face part (thickness part) of the plate shape.

The low-temperature side heat exchanger 3 includes the mesh laminationbody 30 including a plurality of metal mesh plates (e.g., made ofcopper). The low-temperature side heat exchanger 3 includes alow-temperature side annular tube 31 also that is an annular tubesurrounding the side face of the mesh lamination body 30. FIG. 3schematically shows the state where such a low-temperature side annulartube 31 surrounding the side face of the mesh lamination body 30sandwiches the mesh lamination body 30 from both sides at across-section including an inflow port 31 a and an outflow port 31 b.This low-temperature side annular tube 31 has a function of receiving,from the inflow port 31 a, the inflow of cooled fluid (e.g., water) thatis at a relatively low temperature with reference to the heated fluidflowing into the high-temperature side heat exchanger 2 described later,and transmitting cold heat of the cooled fluid to the mesh laminationbody 30 (in other words, transmits heat at the mesh lamination body 30to the cooled fluid) and letting cooled fluid with an increasedtemperature flow out from the outflow port 31 b.

Cold heat transmitted to the mesh lamination body 30 is transmitted tothe working fluid in contact therewith, and is then transmitted to theend face of the heat/acoustic wave conversion component 1 on thelow-temperature side heat exchanger 3 side due to displacement ofacoustic waves to cool the end of the heat/acoustic wave conversioncomponent 1 on the low-temperature side heat exchanger 3 side. To thisend, the metal member 32 is preferably made of a material having largeheat conductivity, which may be made of e.g., copper.

That is the detailed description of the configuration of thelow-temperature side heat exchanger 3, and the heat/acoustic waveconversion unit of the present invention is not limited especially aboutthe details of the low-temperature side heat exchanger, and aconventionally known heat exchanger may be used. The same configurationas that of the high-temperature side heat exchanger 2 described latermay be used.

The side face of the heat/acoustic wave conversion component 1 issurrounded by the interference member 1 a, and FIG. 3 schematicallyshows the cross section of the surrounding interference member 1 a astwo parts that sandwich the heat/acoustic wave conversion component 1from both of right and left sides in the drawing. This interferencemember 1 a has a function as a thermal insulator to avoid heattransmission between the ends of the heat/acoustic wave conversioncomponent 1 on the low-temperature side heat exchanger 3 side and on thehigh-temperature side heat exchanger 2 side via the surroundingenvironment outside of the heat/acoustic wave conversion component 1.

The high-temperature side heat exchanger 2 includes a heat-exchanginghoneycomb structure 20 and a high-temperature side annular tube 21. Theheat-exchanging honeycomb structure 20 has a honeycomb structuresimilarly to the heat/acoustic wave conversion component 1, includingtwo or more cells 20 d, each being a thin-tube like through holepenetrating vertically in FIG. 3, that are partitioned and defined by apartition wall 20 a. The high-temperature side annular tube 21 is anannular tube surrounding the side face of the heat-exchanging honeycombstructure 20, and has a function of receiving, from an inflow port 21 a,the inflow of high-temperature heated fluid (e.g., high-temperatureexhaust gas), transmitting heat of the heated fluid to theheat-exchanging honeycomb structure 20 and letting heated fluid with adecreased temperature flow out from an outflow port 21 b. Then as shownin FIG. 3, the high-temperature side annular tube 21 internally includesa metal or ceramic fin 21 e containing SiC (silicon carbide) as a maincomponent to increase the contact area with the heated fluid.

FIG. 4 is a perspective view showing the appearance of thehigh-temperature side heat exchanger 2 in the heat/acoustic waveconversion unit 100 of FIG. 3, and FIG. 5 is a cross-sectional view ofthe high-temperature side heat exchanger 2, which is a plan viewincluding the inflow port 21 a and the outflow port 21 b of thehigh-temperature side annular tube 21.

As shown in FIG. 4, the high-temperature side heat exchanger 2 includesthe heat-exchanging honeycomb structure 20 that is fitted in a centerhollow part of the annular shape of the high-temperature side annulartube 21. As indicated with thick arrows in FIG. 4, high-temperatureheated fluid (e.g., high-temperature exhaust gas) flows into thehigh-temperature side annular tube 21 from the inflow port 21 a on thelower side of the drawing and flows out from the outflow port 21 b onthe upper side of the drawing. At this time, as indicated with thearrows in FIG. 5, the high-temperature heated fluid flowing in throughthe inflow port 21 a directly hits a circumferential wall 20 b definingthe circular circumference of the heat-exchanging honeycomb structure 20and then is branched off into left and right two sides of thecircumferential wall 20 b and travels along the circumferential wall 20b. Then they join together at the outflow port 21 b to flow out. In thisway, the high-temperature heated fluid directly comes into contact withthe circumferential wall 20 b of the heat-exchanging honeycomb structure20, whereby a lot of heat is directly transmitted from thehigh-temperature heated fluid to the circumferential wall 20 b, and suchheat is transmitted to the partition wall 20 a in the heat-exchanginghoneycomb structure 20 and the working fluid inside of the cells 20 d aswell. In this way, the heat-exchanging honeycomb structure 20 candirectly come into contact with the high-temperature heated fluidbecause the heat-exchanging honeycomb structure 20 is made of a materialhaving high heat resistance and good heat conductivity as describedlater, and such a direct contact with the heated fluid can suppress heatloss and improve heat-exchanging efficiency as compared with the caseincluding another member intervening therebetween.

Although it is preferable that the heat-exchanging honeycomb structure20 directly comes into contact with heated fluid in this way, thepresent invention may have a form in which, instead of such a directcontact of the circumferential wall 20 b of the heat-exchanginghoneycomb structure 20 with high-temperature heated fluid, thecircumferential wall 20 b is surrounded with metal. Especially whenhigh-pressure gas (e.g., inert rare gas such as argon) is used as theworking fluid to transmit acoustic waves, it is preferable to surroundthe circumferential wall 20 b with metal from the viewpoint ofhermetically sealing of such high-pressure gas and avoiding the leakage.In this case, the metal surrounding the circumferential wall 20 b has acircumferential face, on which a metal fin (see fin 21 e in FIG. 3, forexample) is preferably provided so as to protrude in the outwarddirection (radial direction) from the center of the heat-exchanginghoneycomb structure 20 of FIG. 5. This is to increase the contact areawith the high-temperature heated fluid and improve heat-exchangingefficiency. If the contact area with the high-temperature heated fluidis small, exchange of heat between the high-temperature heated fluid andthe high-temperature side heat exchanger 2 is not sufficient, and so theheat-exchanging efficiency of the high-temperature side heat exchanger 2deteriorates. In this way, it is important for the high-temperature sideheat exchanger 2 to maximize the contact area with the high-temperatureheated fluid.

In a most preferable form, another honeycomb structure made of a ceramicmaterial containing SiC (silicon carbide) as a main component is fittedin the tube of the high-temperature side annular tube. This is becausesuch a ceramic material containing SiC (silicon carbide) as a maincomponent has higher heat conductivity at high temperatures than that ofmetal fins, and the contact area with high-temperature gas also can beincreased dramatically. Further, this can avoid a problem of erosion anddeterioration due to high-temperature heated fluid, which can be aproblem for metal fins. The following describes such a preferable form.

FIG. 6 schematically shows one form of a heat/acoustic wave conversionunit including another honeycomb structure fitted in thehigh-temperature side annular tube. FIG. 7 is a schematiccross-sectional view of the high-temperature side heat exchanger takenalong the line A-A of FIG. 6.

In FIGS. 6 and 7, the same reference numerals are assigned to the sameelements as those in FIGS. 3 to 5, and their duplicated descriptions areomitted.

A high-temperature side heat exchanger 2′ in a heat/acoustic waveconversion unit 200 in FIG. 6 includes a heat-exchanging honeycombstructure 20′ and two mutually different high-temperature side annulartubes 211 and 212. The heat-exchanging honeycomb structure 20′ has ahoneycomb structure including two or more cells penetrating horizontallyin the drawing that are partitioned and defined by a partition wall, andtransmits heat transmitted from heated fluid via the two differenthigh-temperature side annular tubes 211 and 212 to the heat/acousticwave conversion component 1. Herein, the heat-exchanging honeycombstructure 20′ is disposed with a distance t from the heat/acoustic waveconversion component 1.

As shown in FIG. 7, the two high-temperature side annular tubes 211 and212 internally include in-tube honeycomb structures 2110 and 2120,respectively, made of a ceramic material containing SiC (siliconcarbide) as a main component. These in-tube honeycomb structures 2110and 2120 both have a honeycomb structure including two or more cellspenetrating horizontally in the drawing that are partitioned and definedby a partition wall. As shown in the arrows of the drawing, heated fluidflowing in the two high-temperature side annular tubes 211 and 212passes through each cell of the in-tube honeycomb structures 2110 and2120, and then flows out. At this time, heat of the heated fluid passingthrough each cell is transmitted to the in-tube honeycomb structures2110 and 2120, and such heat is then transmitted to the heat-exchanginghoneycomb structure 20′ via the wall faces of the high-temperature sideannular tubes 211, 212 and a metal tube (not shown) surrounding the sideface (face of the circumferential wall) of the heat-exchanging honeycombstructure 20′. Although FIG. 7 shows the cross-section of theheat-exchanging honeycomb structure 20′ as a rectangular shape forsimplicity, it may have a circular cross section as in FIGS. 4 and 5,and a substantially similar configuration can be realized when thehigh-temperature side annular tubes 211 and 212 have a shape along thecircle.

In this way, the circumferential wall of the heat-exchanging honeycombstructure 20′ is surrounded with a metal tube, on an outside of whichthe two in-tube honeycomb structures 2110 and 2120 made of a ceramicmaterial containing SiC (silicon carbide) as a main component aredisposed. In this configuration, the heat-exchanging honeycomb structure20′ is not in a direct contact with the heated fluid, and so erosion anddeterioration due to high-temperature heated fluid can be suppressed.When inert rare gas (e.g., argon) is used as the working fluid, aproblem of erosion of the heat-exchanging honeycomb structure 20′ due toworking fluid does not happen. In this case, the heat-exchanginghoneycomb structure 20′ may be made of a metal material having good heatconductivity, such as copper, as well as a ceramic material containingSiC (silicon carbide) as a main component.

Herein, the heat-exchanging honeycomb structure 20′ in FIG. 6 preferablyhas a length L′ of the order of wavelength of acoustic waves generatedfrom oscillations of the working fluid. If the length L′ is too longwith reference to the wavelength of acoustic waves, the heat given tothe working fluid (e.g., inert rare gas) will be insufficient. If thelength L′ is too short with reference to the wavelength of acousticwaves, then working fluid may pass through the heat-exchanging honeycombstructure 20′ from the outside and reach the heat/acoustic waveconversion component 1, and the working fluid at a relatively lowtemperature may cool the end of the heat/acoustic wave conversioncomponent 1 on the high-temperature side heat exchanger sideunfortunately.

FIG. 8 schematically shows another form of the heat/acoustic waveconversion unit of the present invention that is different from theheat/acoustic wave conversion units in FIGS. 6 and 7, and FIG. 9schematically shows still another form of the heat/acoustic waveconversion unit that is different from the heat/acoustic wave conversionunit in FIG. 8.

In the heat/acoustic wave conversion unit of FIG. 8, heated fluid flowsinto the high-temperature side heat exchanger 2A from the upper side ofthe drawing and flows through the high-temperature side heat exchanger2A, and then flows out toward the lower side of the drawing. On theother hand, in the heat/acoustic wave conversion unit of FIG. 9, heatedfluid flows into the high-temperature side heat exchanger 2A′ from theupper side of the drawing and flows through the high-temperature sideheat exchanger 2A′, and then flows out toward the upper side of thedrawing. Herein in both of the heat/acoustic wave conversion units ofFIGS. 8 and 9, cooled fluid flows into the low-temperature side heatexchanger 3A from the upper side of the drawing and flows through thelow-temperature side heat exchanger 3A, and then flows out toward theupper side of the drawing. FIGS. 8 and 9 show the configurationpartially as a perspective view to clarify the internal configurations(configuration including the following two honeycomb structures 22, 23).

The high-temperature side heat exchanger 2A in FIG. 8 and thehigh-temperature side heat exchanger 2A′ in FIG. 9 include apillar-shaped honeycomb structure 23 made of a metal material, and ahollow and round pillar-shaped (in other words, a cylindrical shapehaving a thickness) honeycomb structure 22 made of a ceramic materialcontaining SiC (silicon carbide) as a main component surrounding thehoneycomb structure. At the circumference of the honeycomb structure 23,a metal mesh outer tube 23 a described later, which is made of the samemetal material, is formed integrally with the metal honeycomb structure23. To be precise, a metalized layer, which is described later, ispresent between the two honeycomb structures 22 and 23. These twohoneycomb structures 22 and 23 both have a honeycomb structure includingtwo or more round pillar-shaped cells penetrating in the elongateddirection that are partitioned and defined by a partition wall. Such aconfiguration in FIGS. 8 and 9 also can suppress heat loss and improveheat conversion efficiency.

These embodiments have a honeycomb structure including the honeycombstructure 23 made of a metal material, and instead of this, a meshstructure made up of metal mesh may be used.

FIG. 10 is a cross-sectional view of a high-temperature side heatexchanger having a mesh structure.

The high-temperature side heat exchanger in FIG. 10 includes, inside ofthe honeycomb structure 22 made of a ceramic material containing SiC(silicon carbide) as a main component that is surrounded with a metalouter tube 22 a, a metal mesh member 23′ via a cylindrical metalizedlayer 23 b and a metal mesh outer tube 23 a. Herein the metalized layer23 b is a layer formed by baking of metal such as molybdenum andmanganese, which is a layer to bond the metal mesh outer tube 23 a madeof metal and the honeycomb structure 22 made of ceramic. Theconfiguration in FIG. 10 also can suppress heat loss and improveheat-exchanging efficiency.

Referring back to FIGS. 3 to 5 again, the descriptions are continued inthe following.

As shown in FIG. 3, the end face of the heat-exchanging honeycombstructure 20 on the heat/acoustic wave conversion component 1 side (theupper end face of the heat-exchanging honeycomb structure 20) is in adirect contact with the end face of the heat/acoustic wave conversioncomponent 1 on the high-temperature side heat exchanger 2 side (thelower end face of the heat/acoustic wave conversion component 1).Hereinafter this upper end face of the heat-exchanging honeycombstructure 20 is called a contact face 20 s. Instead of such a directcontact between the heat/acoustic wave conversion component 1 and theheat-exchanging honeycomb structure 20, gap t as in FIG. 6 may bepresent between the heat/acoustic wave conversion component 1 and theheat-exchanging honeycomb structure 20 in the present invention. In thiscase, heat transmitted to the heat-exchanging honeycomb structure 20 istransmitted to working fluid coming into contact with theheat-exchanging honeycomb structure 20, and the heated working fluidcomes into contact with the vicinity of the end face of theheat/acoustic wave conversion component 1 due to displacement of theworking fluid, which corresponds to oscillations of acoustic waves, toheat the vicinity of the end face. This allows the end of theheat/acoustic wave conversion component 1 on the high-temperature sideheat exchanger 2 side to keep a relatively high-temperature state ascompared with the end on the low-temperature side heat exchanger 3 side.

This heat-exchanging honeycomb structure 20 is made of a ceramicmaterial containing SiC (silicon carbide) as a main component. Since aceramic material has high heat resistance, such a material is suitablefor the material of the heat-exchanging honeycomb structure 20 thatdirectly comes into contact with high-temperature heated fluid as statedabove. Further, since a ceramic material containing SiC (siliconcarbide) as a main component has relatively good heat conductivity amongother ceramic materials, such a material is suitable for a function tolet the heat-exchanging honeycomb structure 20 transmit heat to theheat/acoustic wave conversion component 1 as stated above. Note herethat “containing SiC (silicon carbide) as a main component” means thatSiC accounts for 50 mass % or more of the material of theheat-exchanging honeycomb structure 20. At this time, the porosity ispreferably 0 to 10%. It is then preferable that the thickness of thepartition wall 20 a is 0.25 to 0.51 mm and the cell density is 15 to 62cells/cm².

Specific examples of the ceramic material containing SiC as a maincomponent include simple SiC as well as Si impregnated SiC, (Si+Al)impregnated SiC, metal composite SiC, recrystallized SiC, Si₃N₄ and SiC.Among them, Si impregnated SiC and (Si+Al) impregnated SiC arepreferable. This is because Si impregnated SiC has good heatconductivity and heat resistance, and has low porosity although it is aporous body and so is formed densely, and then it can realize relativelyhigh strength as compared with SiC without impregnated Si.

As shown in FIG. 5, the heat-exchanging honeycomb structure 20 has aconfiguration of the triangle cells 20 d that are arranged periodicallywith a period of a constant length in the plane perpendicular to thepenetrating direction of the cells 20 d. As described later, theheat/acoustic wave conversion component 1 to which heat is to betransmitted also has a similar configuration in the honeycomb segmentdescribed later that is a collective form of a plurality of cells 14,and the period of the cells 20 d in the heat-exchanging honeycombstructure 20 is integral multiples of 10 or more of the period of cells14 in the heat/acoustic wave conversion component 1. In this way, thecells 20 d of the heat-exchanging honeycomb structure 20 have the sameshape as that of the cells 14 of the heat/acoustic wave conversioncomponent 1 to which heat is to be transmitted, and the period of thecells 20 d of the heat-exchanging honeycomb structure 20 is integralmultiples of the period of the cells 14 of the heat/acoustic waveconversion component 1, whereby working fluid contained inside the cells20 d of the heat-exchanging honeycomb structure 20 and the cells 14 ofthe heat/acoustic wave conversion component 1 can move smoothly. Theperiod of the cells of the heat-exchanging honeycomb structure 20 islarger than the period of the cells of the heat/acoustic wave conversioncomponent 1 because the cells 14 of the heat/acoustic wave conversioncomponent 1 are required to be very thin through holes to causeself-induced oscillations as stated above. On the other hand, there isno such a request for the cells 20 d of the heat-exchanging honeycombstructure 20, and the heat-exchanging honeycomb structure 20 may play arole of heat exchange simply, and so the period of them is larger thanthe period of the cells 14 of the heat/acoustic wave conversioncomponent 1 by one digit (ten times) or more.

Note here that preferably a honeycomb segment described later of theheat/acoustic wave conversion component 1 has a periodic arrangementwith a period of a constant length, and the period of the cells of theheat-exchanging honeycomb structure 20 is preferably integral divisionsof the period of this honeycomb segment (in other words, the period ofthis honeycomb segment is integral multiples of the period of the cellsof the heat-exchanging honeycomb structure 20). This can suppressblocking of the cells of the heat-exchanging honeycomb structure 20 at aboundary with the neighboring honeycomb segments and so can suppressattenuation of acoustic waves. The integral multiples as stated abovepreferably are 5 to 20 times.

As shown in FIG. 3, the contact face 20 s of the heat-exchanginghoneycomb structure 20 with the heat/acoustic wave conversion component1 is displaced toward the heat/acoustic wave conversion component 1(upper side in the drawing) from a heat-receiving region 21 c where theheat-exchanging honeycomb structure 20 directly comes into contact withhigh-temperature heated fluid to receive heat therefrom, and so does notoverlap with the heat-receiving region 21 c. If the contact face 20 soverlaps with the heat-receiving region 21 c, a temperature may differgreatly between the periphery of an edge of the contact face 20 s closerto the heat-receiving region 21 c and a center region away from theheat-receiving region 21 c. In this case, the end (lower end in FIG. 3)of the heat/acoustic wave conversion component 1 on the heat-exchanginghoneycomb structure 20 side is not heated uniformly, and so the cells ofthe heat/acoustic wave conversion component 1 cause non-uniformself-induced oscillations unfortunately. The heat-exchanging honeycombstructure 20 in FIG. 3 is configured so as not to overlap the contactface 20 s with the heat-receiving region 21 c to avoid such a problem.

As shown in FIG. 5, the heat-exchanging honeycomb structure 20 includesa slit 20 c as a gap part of the circumferential wall 20 b, the slitextending in the penetrating direction of the cells 20 d. FIG. 5 showsthe example of slits 20 c formed at four positions of thecircumferential face of the heat-exchanging honeycomb structure 20. Suchslits 20 c can mitigate thermal stress applied to the circumferentialwall 20 b when high-temperature heated fluid directly comes into contactwith the circumferential wall 20 b, which then can suppress breakage orpeeling-off of the circumferential wall 20 b and the partition wall 20a.

As shown in FIG. 5, the high-temperature side annular tube 21 isprovided with four heat-resistant metal plates 21 d along the extendingdirection of the slits 20 c to fill the gaps at the slits 20 c andextend. These four heat-resistant metal plates 21 d can prevent workingfluid from leaking into the high-temperature side annular tube 21through the four slits 20 c. Note here that the heat-exchanginghoneycomb structure 20 is supported by fitting into these fourheat-resistant metal plates 21 d at an annular center part of thehigh-temperature side annular tube 21. These four heat-resistant metalplates 21 d are provided with fins 21 e (see FIG. 3 also) made of metalor ceramic containing SiC (silicon carbide) as a main component, thefins protruding outward (radial direction) from the center of theheat-exchanging honeycomb structure 20 in FIG. 5.

Next, the following describes the heat/acoustic wave conversioncomponent 1 in FIG. 3 in details.

FIG. 11 is a cross-sectional view of the heat/acoustic wave conversioncomponent 1 in FIG. 3 in a plane perpendicular to the penetratingdirection of the cells 14 of the heat/acoustic wave conversion component1.

As shown in FIG. 11, the heat/acoustic wave conversion component 1includes a plurality of honeycomb segments 15 each being a monolithicconfiguration, a bonding part 12 to bond the honeycomb segments 15mutually, and a circumferential wall 13 that surrounds the circumferenceof the honeycomb structure body including these bonded members.

Each of the honeycomb segments 15 includes a plurality of cells 14, eachbeing a thin-tube like through hole, that are partitioned and defined bya partition wall 11. As described above, hydraulic diameter HD of thecells 14 is one of the important factors to generate acoustic waves byself-induced oscillations, and so the hydraulic diameter HD of the cells14 of each honeycomb segment in the heat/acoustic wave conversioncomponent 1 has a very small value of 0.4 mm or less. Such cells with avery small hydraulic diameter HD can realize a sufficient thermoacousticeffect from the heat/acoustic wave conversion component 1. Conversely ifthe hydraulic diameter HD is larger than 0.4 mm, a very smallthermoacoustic effect only can be realized, and then it becomesdifficult to obtain sufficient amount of electric power and cold heatfrom the power generation system 1000 in FIG. 1 and the cold heatgeneration system 2000 in FIG. 2.

Herein, for a larger thermoacoustic effect, it is advantageous to formas many as possible of the cells having a small hydraulic diameter asstated above. In other words, it is advantageous to have a larger openfrontal area at the end faces of the honeycomb segments 15. Then, theheat/acoustic wave conversion component 1 includes each honeycombsegment having an open frontal area of 60% or more, from which a largerthermoacoustic effect can be obtained. If the open frontal area is lessthan 60%, the number of cells contributing to the thermoacoustic effectis too small, and so a very large thermoacoustic effect cannot beachieved therefrom.

Herein, if the open frontal area is too large, this means too manyhollows in each honeycomb segment, and so durability of each honeycombsegment and accordingly of the heat/acoustic wave conversion component 1as a whole deteriorates. Then the open frontal area at the honeycombsegments 15 is suppressed to be 93% or less. Actually if the openfrontal area exceeds 93%, damage of the honeycomb segments 15 due tothermal distortion and twisting (thermal stress described later)resulting from impacts of generated acoustic waves and a temperaturedifference at both ends of the honeycomb segments cannot be ignored.

In this way, the open frontal area at the end faces of each honeycombsegment in the heat/acoustic wave conversion component 1 that is 60% ormore and 93% or less can achieve adequate balance between a sufficientthermoacoustic effect and sufficient durability. The open frontal areaof 80% or more and 93% or less is preferable in the open frontal area of60% or more and 93% or less.

The open frontal area can be obtained by taking an image of a crosssection perpendicular to the penetrating direction by a microscope, anddetermining the material-part area S1 and the gap-part area S2 from thetaken image of the cross section. Then the open frontal area can beobtained as S2/(S1+S2) based on S1 and S2.

The material making up of each honeycomb segment in the heat/acousticwave conversion component 1 has low heat conductivity of 5 W/mK or less.If the heat conductivity is larger than 5 W/mK, heat is transmittedthrough the partition wall 11 from the high-temperature side heatexchanger 2 side to the low-temperature side heat exchanger 3 side ineach honeycomb segment before heat exchange between the working fluid ineach cell and the partition wall 11 becomes sufficient. As a result, asufficient thermoacoustic effect may not be obtained. On the other hand,such low heat conductivity of 5 W/mK or less leads to sufficient heatexchange between the working fluid in each cell and the partition wall11, and so a sufficient thermoacoustic effect can be obtained. Heatconductivity of 1.5 W/mK or less is preferable in the heat conductive of5 W/mK or less. If the heat conductivity is too small, then the end faceof the heat/acoustic wave conversion component 1 on the high-temperatureside heat exchanger 2 side only has a high temperature locally, meaninga failure to transmit heat to the wall face in the cells and so thedifficulty to generate a thermoacoustic effect. Then, heat conductivityof at least 0.01 W/mK is preferable.

The heat conductivity can be obtained by a temperature gradient method(steady method). Specifically, the heat conductivity can be obtained asfollows. Firstly, a plate-shaped test sample is cut out from a targetfor the heat conductivity measurement, and such a plate-shaped testsample is sandwiched between spacers whose heat conductivity is known(e.g., made of metals, such as copper and stainless steel). Then, oneside thereof is heated to 30° C. to 200° C., and the other side iscooled to 20 to 25° C., whereby a certain temperature difference isgiven in the thickness direction of the test sample. Then, the heat flowrate transmitted is obtained by the temperature gradient in the spacers,and this heat flow rate is divided by the temperature difference tocalculate the heat conductivity.

Let that L denotes the length between both end faces of the honeycombsegment 15, the honeycomb segment 15 has a ratio HD/L of the hydraulicdiameter HD as stated above to the length L that is 0.005 or more andless than 0.02. If HD/L is less than 0.005, the honeycomb segment 15 istoo long as compared with the hydraulic diameter HD. Then working fluidin each cell of the honeycomb segment 15 will be less affected from atemperature difference between both ends of the honeycomb segments. Inthis case, heat exchange between the working fluid in each cell and thepartition wall 11 is not sufficient and so a sufficient thermoacousticeffect cannot be obtained. On the other hand, if HD/L is 0.02 or more,then the honeycomb segment 15 is too short as compared with thehydraulic diameter HD. In this case, heat is transmitted through thepartition wall 11 from the high-temperature side heat exchanger 2 sideto the low-temperature side heat exchanger 3 side in each honeycombsegment before heat exchange between the working fluid in each cell andthe partition wall 11 becomes sufficient. As a result, a sufficientthermoacoustic effect still cannot be obtained. Then, the heat/acousticwave conversion component 1 is configured to have the ratio HD/L of0.005 or more and less than 0.02 in each honeycomb segment, and so heatexchange between the working fluid in each cell and the partition wall11 is sufficient. As a result, the heat/acoustic wave conversioncomponent 1 can have a sufficient thermoacoustic effect.

The heat/acoustic wave conversion component 1 has a bonding structure inwhich the honeycomb segments 15 are mutually bonded with the bondingpart 12 as shown in FIG. 11, whereby the bonding part 12 can exert abuffer effect to thermal stress. When heating and cooling are performedat both ends of the heat/acoustic wave conversion component 1 by thehigh-temperature side heat exchanger 2 and the low-temperature side heatexchanger 3 of FIG. 3, then thermal stress resulting from a differencein the amount of thermal expansion between the both ends typically actson the heat/acoustic wave conversion component 1. Such a bondingstructure allows the bonding part 12 to generate an elastic forceagainst such thermal stress while deforming elastically to some extentand weakening the thermal stress (buffer effect). Then thermal stressacts less directly on the honeycomb segments 15 themselves, and sodamage on the honeycomb segments 15, and accordingly on theheat/acoustic wave conversion component 1 as a whole can be suppressed.

In the heat/acoustic wave conversion component of the present invention,each honeycomb segment may include cells 14 having a shape in a planeperpendicular to the penetrating direction of the cells that are variouspolygons, such as triangles, quadrangles, pentagons and hexagons as wellas ellipses (including a perfect circle shape), where triangles,quadrangles and hexagons and their combinations are preferable. As shownin the enlarged view on the upper right side of the heat/acoustic waveconversion component 1 in FIG. 11 showing the arrangement of the cells14, it is particularly preferable to arrange triangle cells 14periodically in such a perpendicular plane.

Such triangular cells 14 are particularly preferable because, amongvarious polygonal shapes and elliptical cell shapes, triangular cellshapes are the most suitable for the arrangement of a lot of cells whileminimizing the thickness of the partition wall. Note here that, in thecase of a honeycomb structure to load catalyst for exhaust purificationto remove fine particles from exhaust gas of automobiles, if their cellshave corners at acute angles, fine particles easily accumulate at thecorners unfortunately. Then, such a honeycomb structure practically doesnot have triangular cell shapes in many cases, although it can have sucha shape in principle. On the other hand, in the case of a honeycombstructure (honeycomb segment) to exert a thermoacoustic effect, such aproblem does not happen to working fluid (gas such as rare gas) causingself-induced oscillations, and so triangular cell shapes, which are themost suitable to arrange a lot of cells, can be used positively.

Meanwhile, a honeycomb segment of the present invention favorably hasthe same shape as that of the cells so that the shape of the cells isdirectly reflected, because the honeycomb segment is a collective formof a plurality of cells, and from the viewpoint of arranging as many aspossible of cells on the cross section of the heat/acoustic waveconversion component as a whole. For instance, when the cells 14 have atriangular shape as in FIG. 11, then the honeycomb segments 15 also havea triangular shape so that the shape of the cells 14 is directlyreflected. FIG. 11 shows the state where triangle honeycomb segments 15are periodically arranged in a plane of FIG. 11 at a part other than thevicinity of the circumferential wall 13 of the heat/acoustic waveconversion component 1.

Herein, when the cells 14 have a triangular shape, the honeycombsegments may have a hexagonal shape other than a triangular shape. Thisis because a hexagon can be made up of six triangles.

FIG. 12 shows an example where cells have a triangular shape, andhoneycomb segments have a hexagonal shape.

In FIG. 12, the same reference numerals are assigned to the sameelements as those in FIG. 11, and their duplicated descriptions areomitted.

In the heat/acoustic wave conversion component 1′ of FIG. 12, as isunderstood from the arrangement of cells 14 that is indicated on theupper right side of FIG. 12 as an enlarged view, triangular cells 14 areperiodically arranged in a plane perpendicular to the penetratingdirection of the cells 14 in a honeycomb segment 15′. This honeycombsegment 15′ has a hexagonal shape, and a plurality of these hexagonalhoneycomb segments 15′ are periodically arranged in a plane of FIG. 11at a part other than the vicinity of the circumferential wall 13 of theheat/acoustic wave conversion component 1′. Such a form also enables asmany as possible of cells to be arranged on the cross section of theheat/acoustic wave conversion component 1′ as a whole.

Referring back to FIG. 11, the following continues the description ofthe heat/acoustic wave conversion component 1 in FIG. 11. The propertiesof the heat/acoustic wave conversion component 1 described below arecommon to the heat/acoustic wave conversion component 1′ in FIG. 12 aswell.

Preferably in the heat/acoustic wave conversion component 1 in FIG. 11,both of the materials making up the bonding part 12 and thecircumferential wall 13 as stated above have a Young's modulus that isless than 30% of the Young's modulus of the material making up thehoneycomb segments 15, and the material making up the bonding part 12has a thermal expansion coefficient that is 70% or more and less than130% of the thermal expansion coefficient of the material making up thehoneycomb segments 15. Then, the material making up the bonding part 12has heat capacity per unit volume that is 50% or more of the heatcapacity per unit volume of the material making up the honeycombsegments 15.

Such a Young's modulus of the materials making up the bonding part 12and the circumferential wall 13 that is less than 30% of the Young'smodulus of the material making up the honeycomb segments 15 leads to asufficient buffer effect to the thermal stress as stated above. At thistime, if the thermal expansion coefficient and the heat capacity perunit volume of the bonding part 12 and the circumferential wall 13differ greatly from the thermal expansion coefficient and the heatcapacity per unit volume of the material making up the honeycombsegments 15 due to a difference in materials, then a problem such aspeeling-off occurs between the bonding part 12 or the circumferentialwall 13 and the honeycomb segments 15, and then durability againstthermal stress may be degraded in this case also. Then the thermalexpansion coefficient and the heat capacity per unit volume of thebonding part 12 and the circumferential wall 13 within theaforementioned numerical range can lead to sufficient durability againstthermal stress.

The Young's modulus is calculated in the following way. Firstly, aplate-shaped sample having predetermined dimensions is cut out for eachmaterial. The dimensions are those for a plate having a square-shapedface belonging to the range of 10×10 mm to 30×30 mm and a thicknessbelonging to the range of 0.5 to 3 mm, which is common to thesematerials. Let that S denotes the area of the plate-shaped sample (mm²)and t denotes the thickness (mm), then variations Δt (mm) in thethickness of the sample is measured when load W (N) belonging to therange of 0 to 3 MPa is applied to the face of the plate-shaped sample.This load W also is common to these materials. Then, the Young's moduleis calculated by the expression E=(W/S)×(t/Δt), where E denotes theYoung's modulus. Especially in order to obtain the Young's modulus forthe material of the honeycomb segments 15, firstly the Young's modulusis measured for a sample having a honeycomb structure as stated above,and then the measured Young's modulus is converted into the Young'smodulus of the material making up the honeycomb segments 15 (i.e., theYoung's modulus as the material property of the honeycomb segments 15that is irrespective of the honeycomb structure) considering thehoneycomb structure.

The thermal expansion coefficient can be obtained pursuant to the“measurement method of thermal expansion of fine ceramics bythermo-mechanical analysis” that is described in JIS R1618-2002. In thismeasurement, a rod-shaped member having the size specified in JISR1618-2002 is cut out from the honeycomb segments 15 so that the lengthdirection of a rod-shaped member to be measured specified in JISR1618-2002 agrees with the penetrating direction of the cells of thehoneycomb segments 15, and then the thermal expansion coefficient isobtained by the method specified in JIS R1618-2002. The thus obtainedthermal expansion coefficient can be used as a thermal expansioncoefficient of the material in the direction agreeing with the cellpenetrating direction.

The heat capacity per unit volume (e.g., 1 cc) can be obtained asfollows. Firstly, a part of the measurement target is pulverized to be apowder form. Then such a powder-form target is used as a sample, andthen a relationship between input heat and temperature rise of thesample is examined using an adiabatic calorimeter. In this way, the heatcapacity per unit volume of the sample can be obtained. Then, the thusobtained heat capacity per unit volume is multiplied by density (massper unit volume) of the measurement target used as the sample beforepulverization, whereby the heat capacity per unit volume (e.g., 1 cc)can be obtained.

Herein the honeycomb segments 15 preferably include, as a maincomponent, one or two or more in combination of cordierite, mullite,aluminum titanate, alumina, silicon nitride, silicon carbide, and heatresistance resins. Containing “as a main component” means that thematerial accounts for 50 mass % or more of the honeycomb segments 15.Meanwhile, the bonding part 12 and the circumferential wall 13 arepreferably prepared by using a coating material including inorganicparticles and colloidal oxide as a bonding material and an outer coatingmaterial to form and the circumferential wall. Exemplary inorganicparticles include particles made of a ceramic material containing one ortwo or more in combination of cordierite, alumina, aluminum titanate,silicon carbide, silicon nitride, mullite, zirconia, zirconium phosphateand titania, or particles of Fe—Cr—Al-based metal, nickel-based metaland silicon(metal silicon)-silicon carbide based composite materials.Exemplary colloidal oxide includes silica sol and alumina sol.

Preferably in the heat/acoustic wave conversion component 1 of FIG. 11,the bonding width of two honeycomb segments 15 mutually bonded is 0.2 mmor more and 4 mm or less, and the ratio of the total cross-sectionalarea of the bonding part 12 to the cross-sectional area of theheat/acoustic wave conversion component 1 in a plane perpendicular tothe penetrating direction of the cells 14 is 10% or less.

Such a bonding width of two honeycomb segments 15 mutually bonded andratio of the total cross-sectional area of the bonding part 12 to thecross-sectional area of the heat/acoustic wave conversion component 1 inthese numerical ranges can lead to sufficient durability against thermalstress while suppressing a decrease in thermoacoustic effect, resultingfrom a decrease in open frontal area due to the bonding part 12.

In the heat/acoustic wave conversion component 1, each of the pluralityof honeycomb segments 15 preferably has a cross-sectional area in aplane perpendicular to the penetrating direction of the cells 14 that is3 cm² or more and 12 cm² or less.

Such a cross-sectional area of each honeycomb segment in theabove-stated numerical range can lead to adequate balance betweensufficient thermoacoustic effect achieved and sufficient durability.

In the heat/acoustic wave conversion component 1, preferably a crosssection of the heat/acoustic wave conversion component 1 in a planeperpendicular to the penetrating direction of the cells 14 has anequivalent circle diameter D of 30 mm or more and 100 mm or less, andthe ratio L/D of the length L of the honeycomb segment 15 to theequivalent circle diameter D is 0.3 or more and 1.0 or less.

The “equivalent circle diameter” is defined as D in the representationof the cross-sectional area of the heat/acoustic wave conversioncomponent 1 as πD²/4. The ratio L/D of the length L of the honeycombsegment 15 to the equivalent circle diameter D in the numerical range of30 mm or more and 100 mm or less may be 0.3 or more and 1.0 or less,whereby a heat/acoustic wave conversion component having a sufficientthermoacoustic effect and an adequate size can be realized.

Preferably the material making up the honeycomb segments 15 in theheat/acoustic wave conversion component 1 has a ratio of thermalexpansion at 20 to 800° C. that is 6 ppm/K or less.

Such a ratio of thermal expansion at 20 to 800° C. of 6 ppm/K or less ofthe material making up the honeycomb segments 15 can suppress damage onthe honeycomb segments 15 when a temperature difference occurs at theboth ends, and accordingly suppress damage on the heat/acoustic waveconversion component 1. A ratio of thermal expansion of 4 ppm/K or lessis more preferable in the ratio of thermal expansion of 6 ppm/K or less.

Preferably the heat/acoustic wave conversion component 1 has a length Lof the honeycomb segments 15 that is 5 mm or more and 60 mm or less.

Each of the honeycomb segments having a cross sectional area in theaforementioned numerical range can achieve a sufficient thermoacousticeffect.

The following describes a method for manufacturing the heat/acousticwave conversion component 1. The following describes the case where thehoneycomb segments 15 are made of a ceramic material.

Firstly, binder, surfactant, pore former, water and the like are addedto a ceramic raw material to prepare a forming raw material. The ceramicraw material preferably includes one or two or more in combination of acordierite forming raw material, a silicon carbide-cordierite basedcomposite material, aluminum titanate, silicon carbide, asilicon-silicon carbide based composite material, alumina, mullite,spinel, lithium aluminum silicate, and Fe—Cr—Al based alloy. Among them,a cordierite forming raw material is preferable. Herein the cordieriteforming raw material is a ceramic raw material formulated to have achemical composition in the range of 42 to 56 mass % of silica, 30 to 45mass % of alumina and 12 to 16 mass % of magnesia, and forms cordieriteafter firing. The ceramic raw material preferably is contained to be 40to 90 mass % with reference to the forming raw material as a whole.

Exemplary binder includes methyl cellulose, hydroxypropoxyl cellulose,hydroxyethylcellulose, carboxymethylcellulose, or polyvinyl alcohol.Among them, methyl cellulose and hydroxypropoxyl cellulose arepreferably used together. The content of the binder is preferably 2 to20 mass % with reference to the forming raw material as a whole.

The content of water is preferably 7 to 45 mass % with reference to theforming raw material as a whole.

Exemplary surfactant used includes ethylene glycol, dextrin, fatty acidsoap, or polyalcohol. They may be used alone or in combination of two ormore types. The content of the surfactant is preferably 5 mass % or lesswith reference to the forming raw material as a whole.

The pore former is not limited especially as long as it forms pores byfiring. Exemplary pore former includes starch, foamable resin, waterabsorbable resin or silica gel. The content of the pore former ispreferably 15 mass % or less with reference to the forming raw materialas a whole.

Next, a kneaded material is prepared by kneading the forming rawmaterial. A method for preparing a kneaded material by kneading theforming raw material is not limited especially. For instance, a kneaderor a vacuum pugmill may be used for this purpose.

Next, the kneaded material is extruded, whereby a plurality of honeycombformed bodies are prepared, including a partition wall defining aplurality of cells. For the extrusion, a die having a shape inaccordance with the hydraulic diameter of each cell, the open frontalarea, the shape of the honeycomb segments, the cell shape, and theperiod of the cells as stated above is preferably used. A preferablematerial of the die is cemented carbide having wear resistance. Valuesof the hydraulic diameter of each cell, the open frontal area, or thelike of each honeycomb formed body are determined, preferably whileconsidering contraction generated during drying and firing describedlater as well.

Herein the honeycomb segments 15 having a very small hydraulic diameterof each cell and having a large open frontal area (having large celldensity) as stated above to exert a larger thermoacoustic effect cannotbe manufactured by simply using an extrusion method as it is (i.e., bysimply executing a similar manufacturing method using a different die toform high-density pores) that is used for a conventional honeycombstructure to load catalyst for exhaust purification, which is free fromsuch constraints, due to the following two problems.

The first problem is that, during extrusion, kneaded material extrudedat a high temperature adheres to the holes in a forming die, whicheasily generates clogging. This problem is mentioned by Patent Document3 also in paragraph [0021].

The second problem is that a die used for a honeycomb structure as inthe honeycomb segments 15 having a very small hydraulic diameter of eachcell and having a large open frontal area (having large cell density)inevitably includes a very thin and minute part (typically a part ofabout 0.3 mm in thickness). Then, such a minute part often is damaged(e.g., is torn) by viscous friction during kneaded material extrusion.

Then, the manufacturing method of the heat/acoustic wave conversioncomponent 1 has the following configuration to solve these two problems.

For the first problem, prior to the extrusion using a die (hereinaftercalled a real die) corresponding to the honeycomb segments 15 having thehydraulic diameter of each cell that is 0.4 mm or less and the openfrontal area that is 60% or more and 93% or less, i.e., having a verysmall hydraulic diameter of each cell and having a large open frontalarea (having large cell density), a kneaded material is extruded usinganother die (hereinafter called a dummy die) having a very smallthickness of ribs that is 0.04 mm or more and 0.09 mm or less. The“thickness of ribs” here refers to the thickness of the partition wallof the honeycomb formed body, and means a slit width of the die. Eachslit is a hole to discharge the kneaded material and is to determine theshape of each partition wall part at the honeycomb structure to bemanufactured. In the following, the “thickness of ribs” means the slitwidth. The extrusion using such a dummy die can remove beforehand thecomponent of the kneaded material that tends to be a cause of theclogging. Then extrusion by a real die is performed for the kneadedmaterial subjected to the extrusion, whereby clogging as stated abovecan be suppressed.

The second problem is solved by reducing viscosity of the kneadedmaterial used for extrusion greatly as compared with the viscosity of akneaded material used for a conventional honeycomb structure to loadcatalyst for exhaust purification so as to reduce the viscous frictionwhile keeping the range of a shape-holding property (i.e. the shape ofthe formed body is not distorted) of the formed body of the honeycombsegments 15 during extrusion. To reduce the viscosity of kneadedmaterial while satisfying the condition to keep a shape-holding propertyin this way, the ratio of water in the kneaded material has to be morestrictly controlled than in the manufacturing of a conventionalhoneycomb structure to load catalyst for exhaust purification (i.e.,keeping an error between the control target of the water ratio and theactual water ratio in a very narrow range). Specifically, the ratio ofwater in the kneaded material is 40 to 42 parts by mass with referenceto 100 parts by mass of the kneaded material solid component that isused to manufacture the honeycomb segments 15, while the ratio of waterin the kneaded material is 25 to 35 parts by mass with reference to 100parts by mass of the kneaded material solid component that is used tomanufacture a conventional honeycomb structure to load catalyst forexhaust purification. When the ratio of water in the kneaded materialincreases, then viscosity of the kneaded material decreases and adequatefluctuations occur in the shape of the formed body of the honeycombsegments 15. This leads to another advantageous effect that self-inducedoscillations of acoustic waves likely occur.

The following describes a die that is used to prepare a honeycomb formedbody (i.e., extrusion) in the present embodiment. For ease ofexplanation, the following mainly describes the case where cells have aquadrangular shape.

FIG. 13 is a perspective view showing the appearance of a die that isused to prepare a honeycomb formed body in the present embodiment, andFIG. 14 is a perspective view showing the appearance of the die in FIG.13 that is viewed from the opposite side of FIG. 13. FIG. 15 is anenlarged plan view showing a part of the surface of the die in FIG. 13,and FIG. 16 schematically shows a cross section of the die of FIG. 15taken along the line A-A′.

As shown in FIGS. 13 to 16, a die 301 includes a second plate-shapedpart 303, and a first plate-shaped part 307 made of tungsten carbidebased cemented carbide. Herein the second plate-shaped part 303 is madeof at least one type selected from the group consisting of iron, steelmaterials, aluminum alloy, copper alloy, titanium alloy and nickelalloy, and this second plate-shaped part 303 includes a back hole 305 tointroduce the forming raw material of the honeycomb formed body. Thefirst plate-shaped part 307 includes a hole part 311 that is incommunication with the back hole 305, and also includes a slit 309 thatis in communication with the hole part 311 and defines a cell block 313.This first plate-shaped part 307 includes a first layer 307 a disposedon the second plate-shaped part 303 side and a second layer 307 bdisposed on the first layer 307 a. Herein, the hole part 311 is open atboth of the faces of the first layer 307 a, and the slit 309 is open atboth of the faces of the second layer 307 b. FIG. 16 shows the statewhere the hole part 311 has an open end 311 a at a first bonding face310 that agrees with an open end 305 a of the back hole 305 at thesecond bonding face. Such a configuration of the die 301 is to lengthenthe life of the die as described later.

The die 301 preferably has a thickness of 4 to 10 mm. If the thicknessis less than 4 mm, the die may be broken during forming. If thethickness is more than 10 mm, pressure loss is high during forming of ahoneycomb structure, meaning difficulty in forming in some cases.

The second plate-shaped part 303 includes a plate-shaped member made ofat least one type selected from the group consisting of iron, steelmaterials, aluminum alloy, copper alloy, titanium alloy and nickelalloy. Herein steel materials are at least one type selected from thegroup consisting of stainless steel, dies steel and high-speed steel.Among these materials, steel materials are preferable as the material ofthe second plate-shaped part 303, and stainless steel is morepreferable.

In the present application, “at least one type selected from the groupconsisting of iron, steel materials, aluminum alloy, copper alloy,titanium alloy and nickel alloy” may be referred to as “free-machiningmaterial”. The free-machining material is a material that can be easilyground as compared with tungsten carbide based cemented carbide. Sincethe second plate-shaped part 303 does not include the slit 309, wearingis less problematic in the second plate-shaped part 303 than in thefirst plate-shaped part 307. Since the second plate-shaped part 303 ismade of free-machining material, the second plate-shaped part 303 hasexcellent workability as compared with tungsten carbide based cementedcarbide. Further the cost for free-machining material is lower than thatof the tungsten carbide based cemented carbide, and so the manufacturingcost can be reduced.

Stainless steel that is one type of the materials available as thesecond plate-shaped part 303 may be well-known stainless steel. Forinstance, it may be SUS304, SUS303 and the like. The size of the secondplate-shaped part 303 is not limited especially, and it may have adesired size depending on the purpose. Herein when the secondplate-shaped part 303 has a circular plate shape, the diameter of thecircular plate (diameters of one face and the other face) is preferably20 to 40 mm. The thickness of the second plate-shaped part 303 ispreferably 2 to 8 mm. If the thickness is less than 2 mm, it maygenerate deformation and breakage due to stress from forming resistance,and if the thickness is more than 8 mm, forming resistance is excessive,meaning difficulty in extrusion of the formed body.

As described above, the second plate-shaped part 303 includes the backhole 305 to introduce the forming raw material, and the back hole 305 isa through hole (a hole that is open at both faces of the secondplate-shaped part 303) to introduce the forming raw material. When thehoneycomb structure is formed using this die 301, the forming rawmaterial for the honeycomb structure is introduced from the back hole305. The back hole 305 may have any shape as long as it can guide theintroduced forming raw material to the hole part 311 and the slit 309,and the back hole 305 preferably has a circular shape in a cross sectionorthogonal to the flowing direction of the forming raw material(thickness direction of the second plate-shaped part). The open end ofthe back hole 305 preferably has a diameter of 0.15 to 0.45 mm, where0.25 to 0.40 mm is more preferable. Such a back hole 305 can be formedby machine processing, such as electrochemical machining (ECM),electrical discharge machining (EDM), laser processing and drillprocessing, for example. Among these methods, electrochemical machining(ECM) is preferable because ECM can form the back hole 305 effectivelyand precisely. The space in the back hole is preferably in around-pillar shape. In this case, the diameter (diameter of the backhole) in a cross section orthogonal to the flowing direction of theforming raw material (thickness direction of the second plate-shapedpart) in the back hole can have a constant value. In this case, thediameter of the back hole is equal to the diameter of the open end ofthe back hole at the second bonding face. The number of back holes isnot limited especially, which can be decided appropriately depending onthe shape of the honeycomb structure to be manufactured, for example.When the cells have a triangular shape, then the back holes preferablyare disposed at all of the positions corresponding to the partition wallintersections, and when the cells have a quadrangular shape, then theback holes are preferably disposed at alternate intersections of thehoneycomb partition wall in a staggered pattern.

The first plate-shaped part 307 includes a plate-shaped member made oftungsten carbide based cemented carbide. The width of the slit 309 isvery narrow as compared with the diameter of the back hole 305. Thismeans that, when the forming raw material is extruded, pressure in theback hole 305 is increased and stress concentrates on the slit 309,which often leads to problems of wearing and deformation, for example.Then, the first plate-shaped part 307 is made of tungsten carbide basedcemented carbide that is a material having wear resistance. Herein,“tungsten carbide based cemented carbide (cemented carbide)” is an alloywhere tungsten carbide and a bonding material are sintered. The bondingmaterial is preferably at least one type of metal selected from thegroup consisting of cobalt (Co), iron (Fe), nickel (Ni), titanium (Ti)and Chromium (Cr). Such tungsten carbide based cemented carbide hasespecially excellent wear resistance and mechanical strength.

The size of the first plate-shaped part 307 is not limited especially,and it may have a desired size in accordance with the purpose. Hereinwhen the first plate-shaped part 307 has a circular plate shape, thediameter of the circular plate is preferably 20 to 40 mm. When the firstplate-shaped part 307 and the second plate-shaped part 303 have acircular plate shape, then the diameter of the first plate-shaped part307 is 90 to 100% of the diameter of the second plate-shaped part 303.The thickness of the first plate-shaped part 307 is preferably 0.3 to1.2 mm, where 0.5 to 0.9 mm is more preferable. The thickness of thefirst plate-shaped part 307 is preferably 0.05 to 2 times the thicknessof the second plate-shaped part 303.

As described above, the first plate-shaped part 307 includes the firstlayer 307 a disposed on the second plate-shaped part 303 side and thesecond layer 307 b disposed on the first layer 307 a. Since the die 301at the first plate-shaped part includes these two layers of the firstlayer 307 a and the second layer 307 b, stress during extrusion can bemitigated, and so breakage can be prevented. The first layer 307 a andthe second layer 307 b may be made of the same type of materials or ofdifferent types of materials.

In this way, the first layer 307 a is one layer making up the firstplate-shaped part 307, and is disposed on the second plate-shaped part303 side. Herein, the first layer 307 a includes the hole part 311. Thefirst layer 307 a preferably is a layer made of cemented carbide havingVickers hardness of 2,000 to 3,000 HV and having the Young's modulus of600 to 800 GPa. When the first layer 307 a has such Vickers hardness andYoung's modulus, it can be a layer having hardness and toughness thatcan resist the stress applied to the hole part 311. Then problems suchas breakage of the first plate-shaped part 307, which may result fromthe stress from the forming raw material flowing into the hole part 311from the back hole 305, can be prevented, and so the life of the die canbe lengthened. The hole part 311 is open at both faces of the firstlayer 307 a.

The first layer 307 a preferably has Vickers hardness of 2,000 to 3,000HV, where 2,000 to 2,200 HV is more preferable. With such predeterminedVickers hardness, the first layer 307 a can have hardness so as toresist the stress from the ceramic raw material flowing into the holepart 311 from the back hole 305. Then wearing of the hole part 311 canbe prevented. If the Vickers hardness of the first layer 307 a is lessthan 2,000 HV, wearing may occur due to the lack of strength. If theVickers hardness of the first layer 307 a exceeds 3,000 HV, it is toohard, and so the first layer 307 a may easily break. The first layer 307a preferably has the Young's modulus of 600 to 800 GPa, where 600 to 700GPa is more preferable. This can prevent breakage of the first layer 307a. If the Young's modulus of the first layer 307 a is less than 600 GPa,the toughness is too small, which may cause problems such as breakage.If the Young's modulus exceeds 800 GPa, the toughness is too large,which may lead to the risk of deformation of the hole part 311. When thehoneycomb structure is formed using a die having the deformed hole part311, then distortion occurs at the honeycomb structure and theformability deteriorates.

As described above, the second layer 307 b is one layer making up thefirst plate-shaped part 307, and is disposed on the first layer 307 a.The second layer 307 b includes the slit 309, and the slit 309 is openat both faces of the second layer 307 b. Herein “both faces of thesecond layer 307 b” mean both faces including the face of the secondlayer 307 b in contact with (bonded to) the first layer 307 a and theface on the opposite side (rear side) of the face in contact with thefirst layer 307 a. In FIG. 16, the discharge port of the forming rawmaterial at the slit 309 is indicated as an open end 309 a of the slit309. The second layer 307 b preferably has Vickers hardness of 500 to3,000 HV and the Young's modulus of 400 to 700 GPa. When the secondlayer 307 b has such Vickers hardness and Young's modulus, it can be alayer having sufficient hardness and toughness that can resist thestress applied to the slit 309. Then deformation and wearing of the slit309 can be prevented.

The second layer 307 b preferably has Vickers hardness of 500 to 3,000HV, where Vickers hardness of 2,000 to 3,000 HV is more preferable. SuchVickers hardness can suppress wearing of the second layer 307 b. If theVickers hardness of the second layer 307 b is less than 500 HV, wearingmay occur easily due to the lack of hardness. If the Vickers hardnessexceeds 3,000 HV, the second layer 307 b may easily break.

The second layer 307 b preferably has the Young's modulus of 400 to 700GPa, where the Young's modulus of 500 to 700 GPa is more preferable.Such Young's modulus of the second layer 307 b makes the layer hard tobreak. If the Young's modulus of the second layer 307 b is less than 400GPa, problems such as breakage easily occur due to too small toughness.If the Young's modulus exceeds 700 GPa, then the toughness is too large,and so the second layer 307 b easily is deformed.

It is preferable that, in the die 301, the Vickers hardness and theYoung's modulus of the second layer 307 b are larger than the Vickershardness and the Young's modulus of the first layer 307 a. That is, itis preferable that the Vickers hardness of the second layer 307 b islarger than the Vickers hardness of the first layer 307 a, and theYoung's modulus of the second layer 307 b is larger than the Young'smodulus of the first layer 307 a. In such a relationship, the secondlayer 307 b including the slit 309 hardly becomes worn, and the firstlayer 307 a including the hole part 311 hardly breaks. Then, the life ofthe die can be lengthened more due to the second layer 307 b suppressingwearing and the first layer 307 a suppressing breakage.

In the die 301, it is preferable that the Vickers hardness of the secondlayer 307 b is larger than the Vickers hardness of the first layer 307 aby 1,000 to 2,500 HV, and the Young's modulus of the second layer 307 bis larger than the Young's modulus of the first layer 307 a by 50 to 300GPa. Then, the first plate-shaped part 307 can have the second layer 307b having wear resistance and the first layer 307 a having high toughnessreliably, and so the life of the die can be lengthened.

The thickness of the first layer 307 a is preferably 0.1 to 5 mm, andthe thickness of the first layer 307 a is 0.2 to 5 mm more preferably.Such a range of the thickness of the first layer 307 a can suppresswearing of the second plate-shaped part effectively. If the thickness ofthe first layer 307 a is less than 0.1 mm, the second plate-shaped parteasily becomes worn. If the thickness of the first layer 307 a exceeds 5mm, pressure during extrusion may increase too high due to such a thickdie.

The thickness of the second layer 307 b is preferably 0.3 to 4 mm, andthe thickness is 1 to 4 mm more preferably. Such a range of thethickness of the second layer 307 b can suppress deformation of thehoneycomb structure after extrusion. If the thickness of the secondlayer 307 b is less than 0.3 mm, the honeycomb structure after extrusionmay be deformed, and the second layer 307 b may become worn or bedeformed. If the thickness of the second layer 307 b exceeds 4 mm, thenthe second layer 307 b is too thick and so the depth of the slit (thelength of the slit in the extruding direction of the forming rawmaterial) is too large, so that pressure during extrusion becomes toohigh. Further, a part surrounded by the slit is extremely long and thin,and the part may be torn due to friction with kneaded material. In orderto prevent such events, a deep slit is not allowed. On the other hand,when the slit is shallow in an adequate degree, then relativefluctuations in the slit depth increase between a plurality of slits. Asa result, the honeycomb structure after extrusion also can have adequatefluctuations in shape, and so self-induced oscillations of acousticwaves easily occur.

As stated above, the first plate-shaped part 307 includes the slit 309that is in communication with the hole part 311 and is to form theforming raw material. The slit 309 is a gap (cut) formed in the firstplate-shaped part 307. The forming raw material introduced from the backhole 305 enters the slit 309 in the die, and then the forming rawmaterial is pushed out from the open end 309 a of the slit 309, wherebya formed body in a honeycomb shape can be formed.

As stated above, the slit 309 is open at both faces of the second layer307 b. Although the slit 309 may be formed at the second layer 307 bonly, it is preferable that the slit is formed at the first layer 307 aas well. When it is formed at the first layer 307 a, the slit 309 formedat the second layer 307 b is extended to the first layer side so as tobe formed at the first layer 307 a preferably. In this case, the slit309 at the first layer 307 a is formed at the face of the first layer307 a in contact with the second layer 307 b. Then in this case, thedepth of the slit 309 is larger than the thickness of the second layer307 b. It is preferable that the depth of the slit 309 is 0.3 to 1.0 mm,where 0.4 to 0.8 mm is more preferable. It is preferable that the depthof the slit 309 at a part extended to the first layer side is 0.1 to 0.5mm, where 0.2 to 0.5 mm is more preferable. This can form a formed bodyof a favorable honeycomb shape. It is preferable that the width of theslit 309 is 0.03 to 0.05 mm, where 0.04 to 0.05 mm is more preferable.

As described above, the first layer 307 a of the first plate-shaped part307 includes the hole part 311 therein, where this hole part 311 is incommunication with the back hole 305 formed at the second plate-shapedpart 303 and the slit 309 formed at the first plate-shaped part 307. Thehole part 311 is a through hole as well that is formed at the firstlayer 307 a of the first plate-shaped part 307. That is, the hole part311 is a through hole that is open at the face of the second layer 307 bon the side in contact with the second plate-shaped part 303 (the firstbonding face 310 of the first plate-shaped part 307) and is open at theface of the second layer 307 b in contact with the first layer 307 a(the other face 307 ba of the second layer). As shown in FIG. 16, thefirst bonding face 310 is a face of the first plate-shaped part 307 thatis bonded (in contact with) to the second plate-shaped part 303. Such ahole part 311 allows a forming raw material introduced from the backhole 305 formed at the second plate-shaped part 303 to pass through thehole part 311 and enter the slit 309. Then the forming raw material ispushed out from the open end 309 a of the slit 309, whereby a honeycombshaped formed body (honeycomb structure) can be formed. It is preferablethat the depth h of the hole part 311 (see FIG. 16) is 0.1 to 4 mm,where 0.2 to 3 mm is more preferable. Such a range of the depth h of thehole part 311 can suppress wearing at the second plate-shaped part 303effectively. If the depth h of the hole part is less than 0.1 mm, thestrength of the first plate-shaped part 307 easily deteriorates duringextrusion of the forming raw material. If the depth h of the hole partexceeds 4 mm, it tends to be difficult to form the hole part byprocessing the first plate-shaped member during preparation of the die.Herein, the depth h of the hole part 311 is a distance from the firstbonding face 310 of the first plate-shaped part 307 to the other face307 ba of the second layer 307 b as shown in FIG. 16. Herein, the depthof the hole part 311 equals the thickness of the first layer 307 a. Itis preferable that the diameter of the open end 311 a of the hole part311 is 0.15 to 0.4 mm, where 0.2 to 0.4 mm is more preferable. The holepart 311 may be formed by machine processing, such as electrochemicalmachining (ECM), electrical discharge machining (EDM), laser processingand drill processing, for example. Among these methods, electrochemicalmachining (ECM) is preferable because it can form the hole part 311effectively and precisely. The space in the hole part 311 is preferablyin a round-pillar shape. In this case, the diameter (diameter of thehole part 311) in a cross section orthogonal to the flowing direction ofthe forming raw material (thickness direction of the first plate-shapedpart) in the hole part 311 can have a constant value. At this time, thediameter of the hole part 311 is equal to the diameter of the open end311 a of the hole part at the first bonding face 310. The number of thehole parts 311 is preferably the same number as that of the back holes.

As shown in FIG. 16, the die 301 is formed so that the diameter dl ofthe open end 311 a (circle) of the hole part 311 at the first bondingface 310 is the same size as that of the diameter D1 of the open end 305a (circle) of the back hole at the second bonding face 306. As shown inFIG. 16, the second bonding face 306 is a face of the secondplate-shaped part 303 that is bonded to (in contact with) the firstplate-shaped part 307. The open end 311 a of the hole part 311 at thefirst bonding face 310 is an inlet part of the through hole (inflow partof the forming raw material) that is open at the first bonding face 310.The open end 305 a of the back hole 305 at the second bonding face 306is an outlet part (outlet part of the forming raw material) on thesecond bonding face 306 side that is open at the second bonding face 306of the back hole 305. As the forming raw material passes through thisoutlet part, it is then supplied to the hole part 311.

Herein it is preferable that the die includes a retainer plateconfiguration to fix the die for extrusion.

FIG. 17 shows an example of the retainer plate configuration.

In the retainer plate configuration of FIG. 17, the forming raw materialis pushed out in the direction of the downward arrow in FIG. 17. At thistime, a rear retaining part 403 can adjust the amount of kneadedmaterial that flows in. A die 401 is fixed by a retainer 402, and aforming raw material that is pushed out from a gap 405 between the die401 and the retainer 402 defines a circumferential part of a honeycombformed body 404 while being adjusted by an inclined face 406 and anopposed face 407.

FIG. 18 shows another example of the retainer plate configuration thatis different from FIG. 17.

In a retainer plate configuration 550 of FIG. 18, the forming rawmaterial is pushed out in the direction of the downward arrow in FIG.18. This retainer plate configuration 550 includes a back hole 553 tosupply a forming raw material, a die 554 having a slit 552 to push outthe forming raw material and a retaining plate 555 that is disposeddownstream of the die 554. The die 554 includes an inside part 571 and acircumference part 572. The inside part 571 protrudes toward thedownstream (downward in FIG. 18) to define a step height 575 with thecircumference part 572, and this inside part 571 is provided with a slit573 to form a honeycomb structure. The circumference part 572 is thenprovided with a slit 574 that is shorter than the slit 573. Between thedie 554 and the retaining plate 555, a gap part 557 to form the outerwall of the honeycomb structure is formed. Herein a retaining jig 558and a rear-retaining plate 559 are holders to set the die 554 and theretaining plate 555.

During extrusion using the retainer plate configuration 550 in FIG. 18,the forming raw material is pushed out from the upstream side of the die554 (above in FIG. 18) toward the downstream via the die 554 by anextruder (not shown). The forming raw material 561 that is pushed outfrom the slit 573 at the inside part 571 of the die 554, the slit beingopen on the downstream side, is formed to be a honeycomb structureincluding a lot of cells. On the other hand, the forming raw material561 that is pushed out from the slit 574 at the circumference part 572of the die 554 has a crushed honeycomb shape by the action at the gappart 557, and changes the traveling direction from the pushing-outdirection to the direction toward the step height 575 and changes againthe traveling direction to the pushing-out direction at the place wherethe retaining plate 555 is open so as to form the outer wall surroundingthe cells.

FIG. 19 shows still another example of the retainer plate configuration.

FIG. 20 shows a further example of the retainer plate configuration thatis different from FIG. 19.

The retainer plate configuration in FIG. 19(a) includes a die 604 havingslits 602 to form the periodic arrangement of regular triangles as shownin FIG. 19(b). This die 604 is to form a honeycomb structure having aregular triangular cell shape, which is fixed by a retaining plate 605.Herein the slits 602 are in communication with back holes 603. In thisretainer plate configuration, the shape (dimensions) of the honeycombformed body to be formed is determined by the length L1 of the slits602, the length L2 that is a difference between the length L1 of theslits 602 and the height of a step height 615, the width W of the slits602 and the distance d between the retaining plate 605 and the stepheight 615.

FIG. 20 shows a further example of the retainer plate configuration thatis different from FIG. 19.

The retainer plate configuration in FIG. 20(a) includes a die 704 havingslits 702 to form the periodic arrangement of squares as shown in FIG.20(b). This die 704 is to form a honeycomb structure having a squarecell shape, which is fixed by a retaining plate 705. Herein the slits702 are in communication with back holes 703. In this retainer plateconfiguration also, the shape (dimensions) of the honeycomb formed bodyto be formed is determined by the length L1 of the slits 702, the lengthL2 that is obtained by subtracting the height of a step height 715 fromthe length L1 of the slits 702, the width W of the slits 702 and thedistance d between the retaining plate 705 and the step height 715.

In both of the retainer plate configurations in FIG. 19 and FIG. 20, itis preferable that the length L1 of the slits 702 is 0.3 to 1.0 mm,where 0.4 to 0.8 mm is more preferable. Then it is preferable that thelength L2 as the difference is 0.1 to 0.5 mm.

The following continues the description on the following processing forthe plurality of honeycomb formed bodies that are obtained by theextrusion.

Preferably the thus obtained plurality of honeycomb formed bodies aredried before firing. A method for drying is not limited especially, andexemplary methods include an electromagnetic wave heating method such asmicrowave heat-drying and high-frequency induction heating drying and anexternal heating method such as hot air drying and superheated steamdrying. After a certain amount of water may be dried by anelectromagnetic wave heating method, followed by an external heatingmethod to dry the remaining water. In this case, it is preferable that,after 30 to 90 mass % of water with reference to the water amount beforedrying is removed by an electromagnetic heating method, followed by anexternal heating method to reduce water amount to 3 mass % or less. Apreferable electromagnetic wave heating method includes inductionheating drying, and a preferable external heating method includes hotair drying.

If the length of the honeycomb formed body in the cell penetratingdirection is not a desired length, it is preferable to cut both of theend faces (end parts) to have the desired length. Although a method forcutting is not limited especially, exemplary method includes a methodusing a circular saw cutter.

Next, the plurality of honeycomb formed bodies are fired to complete aplurality of honeycomb segments 15. It is preferable to performcalcination before firing to remove the binder and the like. Thecalcination is preferably performed at 400 to 500° C. for 0.5 to 20hours in the ambient atmosphere. A method for calcination or firing isnot limited especially, and they may be performed using an electricfurnace, a gas furnace, or the like. As the firing conditions, it ispreferably heated at 1,300 to 1,500° C. for 1 to 20 hours in an inertatmosphere of nitrogen, argon, or the like when a silicon-siliconcarbide based composite material is used, for example. When anoxide-based material is used, it is preferably heated at 1,300 to 1,500°C. for 1 to 20 hours in an oxygen atmosphere.

Next, the plurality of honeycomb segments 15 are arranged so that theirside faces are opposed, which are then bonded with a bonding materialthat is a material before solidification of the bonding part 12,followed by drying. A method to apply the bonding material to the sidefaces of the honeycomb segments is not limited especially, and aconventional method using a brush may be used, and it is preferable toapply it on the opposed side faces as a whole. This is because thebonding part 12 plays a role of buffering (absorbing) thermal stress asstated above, in addition to the role of bonding the honeycomb segmentsmutually. Herein, the bonding material may be slurry, for example, whichis prepared by adding an additive such as organic binder, foamable resinor dispersing agent to a raw material including inorganic particles andcolloidal oxide, to which water is added, followed by kneading. Hereinexemplary inorganic particles include particles made of a ceramicmaterial containing one or two or more in combination of cordierite,alumina, aluminum titanate, silicon carbide, silicon nitride, mullite,zirconia, zirconium phosphate and titania, or particles ofFe—Cr—Al-based metal, nickel-based metal and silicon (metalsilicon)-silicon carbide based composite materials. Exemplary colloidaloxide includes silica sol and alumina sol.

Next, the circumferential part of these plurality of honeycomb segments15 mutually bonded with the bonding material as a whole is cut so as toachieve a desired cross-sectional shape of the heat/acoustic waveconversion component 1. Then, an outer coating material is applied tothe circumferential face of the plurality of honeycomb segments 15 aftercutting as a whole, followed by drying. Herein, the outer coatingmaterial used may be the same material as that of the bonding material.A method for applying the outer coating material is not limitedespecially, and for example, the coating material may be coated with arubber spatula, for example, while rotating the honeycomb segment bondedbody on a wheel.

Through this process, the heat/acoustic wave conversion component 1 isfinally completed.

Next, the following describes a method for manufacturing thehigh-temperature side heat exchanger 2 in FIG. 3.

The heat-exchanging honeycomb structure 20 in the high-temperature sideheat exchanger 2 of FIG. 3 can be manufactured by a manufacturing methodsimilar to the method for manufacturing the heat/acoustic waveconversion component 1 as stated above, other than that mixture ofcarbon powder (e.g., graphite powder) with SiC powder is used as theceramic raw material, a die suitable for a honeycomb formed body havinga relatively large hydraulic diameter of cells is used as the die forextrusion, and the process for segment bonding is omitted (i.e., ahoneycomb structure is manufactured using a single honeycomb segment).

To manufacture this heat-exchanging honeycomb structure 20, for example,including a Si impregnated SiC composite material as a main component,it is preferable that a kneaded material prepared by mixing SiC powderwith carbon powder and kneading for adjustment is formed to be ahoneycomb formed body, then drying and sintering processing areperformed thereto, and then molten silicon (Si) is impregnated in thishoneycomb formed body. Such processing can form a configuration wherecoagulation of metal Si (metal silicon) surrounds the surface of SiCparticles after the sintering processing, and SiC particles are mutuallybonded via metal Si. Such a configuration can achieve high heatdurability and heat conductivity in spite of the dense configurationwith small porosity.

In addition to the molten silicon (Si), other metals such as Al, Ni, Cu,Ag, Be, Mg, and Ti may be used for impregnation. In this case, aftersintering, coagulation of metal Si (metal silicon) and other metals usedfor impregnation surrounds the surface of SiC particles, and SiCparticles are mutually bonded via metal Si and other metals used forimpregnation in the formed configuration. Such a configuration also canachieve high heat durability and heat conductivity in spite of the denseconfiguration with small porosity.

As the outer coating material of the heat-exchanging honeycomb structure20 as well, particles of silicon (metal silicon)-silicon carbide basedcomposite material is preferably used for the same reason as statedabove, among the particles made of the materials as stated above as thecandidates of inorganic particles of the material of the outer coatingmaterial (the material of the bonding material of the heat/acoustic waveconversion component 1).

It is preferable to perform slit formation processing to form a slit inthe cell penetrating direction at the circumferential wall formed by theapplication of the outer coating material. When the slit formationprocessing is performed, a heat resistant metal plate 21 d and a fin 21e may be formed when the high-temperature side annular tube 21 ismanufactured as described below.

The high-temperature side annular tube 21 on the high-temperature sideheat exchanger 2 in FIG. 3 is prepared by forming a material of highheat resistance to be an annular shape (herein, the annular shape suchthat a part of the wall face on the center side is partially omitted sothat, when being coupled with the heat-exchanging honeycomb structure20, a part of the circumferential wall of the heat-exchanging honeycombstructure 20 is exposed in the high-temperature side annular tube). Sucha material of high heat resistance is not limited especially, andspecific examples include metal such as stainless steel and copper ofhigh heat resistance and ceramic materials (e.g., those listed as thematerials of the heat/acoustic wave conversion component 1 and theheat-exchanging honeycomb structure 20).

The high-temperature side heat exchanger 2 in FIG. 3 is completedbasically by assembling the heat-exchanging honeycomb structure 20 at acenter part that is a hole at the annular shape of the high-temperatureside annular tube 21.

Next the following describes a method for manufacturing thelow-temperature side heat exchanger 3 in FIG. 3. When a conventionallyknown heat exchanger is used as the low-temperature side heat exchanger3, a method for manufacturing such a conventionally known heat exchangercan be used. When the device having the same configuration as that ofthe high-temperature side heat exchanger 2 stated above is used as thelow-temperature side heat exchanger 3, the same manufacturing method asthat of the high-temperature side heat exchanger 2 as stated above canbe used.

As other members of the heat/acoustic wave conversion unit 100 in FIG.3, e.g., the metal member 32, the housing 100 a, and the interferencemember 1 a, those conventionally known can be used, and they can bemanufactured by a conventionally known method.

EXAMPLES

The following describes the present invention more specifically by wayof examples, and the present invention is by no means limited to theseexamples.

Example 1

In Example 1, cordierite forming raw material was used as the ceramicraw material. Then 35 parts by mass of dispersing medium, 6 parts bymass of organic binder, and 0.5 parts by mass of dispersing agent wereadded to 100 parts by mass of the cordierite forming raw material,followed by mixing and kneading to prepare a kneaded material. Thecordierite forming raw material used included 38.9 parts by mass of talcof 3 μm in average particle size, 40.7 parts by mass of kaolin of 1 μmin average particle size, 5.9 parts by mass of alumina of 0.3 μm inaverage particle size, and 11.5 parts by mass of boehmite of 0.5 μm inaverage particle size. Herein the average particle size refers to amedian diameter (d50) in the particle distribution of each raw material.

Water was used as the dispersing medium. Hydroxypropylmethylcellulosewas used as the organic binder. Ethylene glycol was used as thedispersing agent.

Next, the thus obtained kneaded material was extruded using a die, sothat a plurality of honeycomb formed bodies each including triangularcells and having a hexagonal overall shape were prepared. During thisextrusion, prior to the extrusion using a regular die corresponding tothe honeycomb segments of Example 1, the kneaded material was extrudedusing a dummy die of about 0.07 mm in rib thickness. Then, using thekneaded material after the extrusion using this dummy die, extrusionusing the real die was executed. At this time, the ratio of water in thekneaded material used for the extrusion using the real die was strictlycontrolled in the kneaded material component so that it was 41 parts bymass (error was within ±1 part by mass) with reference to 100 parts bymass of the kneaded material solid component.

At this time, the retainer plate configuration in FIG. 19 was used asthe retainer plate configuration for the die. In this retainer plateconfiguration, the length L1 (see FIG. 19) of the slit was 0.5 mm, andthe length L2 (see FIG. 19) obtained by subtracting the height of thestep height from the slit length L1 was 0.2 mm. Then, the width W (seeFIG. 19) of the slit was 0.05 mm, and the distance d (see FIG. 19)between the retaining plate and the step height was 0.5 mm.

Then, these plurality of honeycomb formed bodies were dried by amicrowave dryer, and then were dried completely by a hot-air drier, andthen both end faces of the honeycomb formed body were cut so as toadjust the length of the honeycomb formed body in the cell penetratingdirection. Such a honeycomb formed body was dried by a hot-air drier,and then was fired at 1,445° C. for 5 hours, whereby the honeycombsegments were completed.

Next, the plurality of honeycomb segments were arranged so that theirside faces are opposed, which were then bonded with a bonding materialthat was a material before solidification of the bonding part 12,followed by drying. An application method at this time was using abrush, and it was applied on the opposed side faces as a whole. Thebonding material was slurry prepared by adding organic binder, foamableresin and dispersing agent to a raw material including cordieriteparticles and silica sol, to which water was added and kneaded.

Next, the circumferential part of these plurality of honeycomb segmentsmutually bonded with the bonding material as a whole was cut to have around-pillar shape. Then, an outer coating material was applied to thecircumferential face of the plurality of honeycomb segments 15 aftercutting as a whole, followed by drying. An application method at thistime was using a rubber spatula, while rotating the plurality ofhoneycomb segments after cutting as a whole on a wheel. The outercoating material used may be the same material as that of the bondingmaterial.

Through this process, the heat/acoustic wave conversion component ofExample 1 was finally completed.

From the thus completed heat/acoustic wave conversion component ofExample 1, one honeycomb segment was chosen at random. Then, as for thishoneycomb segment, the following properties were measured, including:the hydraulic diameter HD of the cells; the open frontal area; the heatconductivity of the material; the length L between both end faces; theYoung's modulus of the material; the thermal expansion coefficient ofthe material (at room temperatures); the heat capacity per unit volumeof the material; and the cross-sectional area in a plane perpendicularto the cell penetrating direction. The hydraulic diameter HD of thecells was obtained as follows. That is, an enlarged photo of the crosssection of the one honeycomb segment in a plane perpendicular to thecell penetrating direction was taken, and 10 cells were selected atrandom in this honeycomb segment. Then, the hydraulic diameter of eachwas calculated by the expression to define the hydraulic diameter:HD=4×S/C, where S denotes the cross-sectional area of the cell and Cdenotes the perimeter of this section, and then average of them wascalculated as the hydraulic diameter.

At the bonding part, the Young's modulus of the material (the same asthe Young's modulus of the circumferential wall), the thermal expansioncoefficient of the material (at room temperatures), the heat capacityper unit volume of the material, the width of the bonding part betweenneighboring honeycomb segments, and the total cross-sectional area atthe bonding part in a plane perpendicular to the cell penetratingdirection were measured.

Then, the diameter and the cross-sectional area of the heat/acousticwave conversion component were measured in a plane perpendicular to thecell penetrating direction.

Based on the measurement values obtained through the measurement asstated above, the following fourteen types of parameters were obtained.The following fourteen types of parameters include ones that are notindependent mutually and change together with other parameters, but suchparameters also are described for the sake of descriptions.

(1) hydraulic diameter HD of the cells in a plane perpendicular(perpendicular plane) to the cell penetrating direction, (2) openfrontal area at the end faces of honeycomb segment, (3) heatconductivity of honeycomb segment, (4) thermal expansion coefficient ofhoneycomb segment, (5) ratio of the Young's modulus at thecircumferential wall to the Young's modulus of honeycomb segment, (6)cross-sectional area of one honeycomb segment in the perpendicularplane, (7) diameter D of the heat/acoustic wave conversion component inthe perpendicular plane, (8) ratio L/D of the length L of honeycombsegment to the diameter D of the heat/acoustic wave conversioncomponent, (9) length L of honeycomb segment, (10) ratio HD/L of thehydraulic diameter HD of the cells to the length L of honeycomb segment,(11) ratio of Young's modulus at the bonding part to Young's modulus ofhoneycomb segment, (12) ratio of the thermal expansion coefficient atbonding part to the thermal expansion coefficient of honeycomb segment,(13) ratio of the heat capacity per unit volume at the bonding part tothe heat capacity per unit volume of honeycomb segment, and (14) widthof the bonding part between neighboring honeycomb segments.

Table 1 describes the values of parameters from (1) to (9) that do notdirectly relate to the bonding part among these fourteen parameters forthe heat/acoustic wave conversion component of Example 1, and Table 2describes the values of parameters from (10) to (14) that relate to thebonding part. Table 2 describes the segmented structure (bonded type ormonolithic type) and the shapes of the cells and segments in addition tothe value of parameters from (10) to (14).

TABLE 1 Heat/acoustic Segment length Cell Segment SegmentCircumferential Segment wave L/heat/acoustic hydraulic open Segmentthermal wall Young's cross- conversion wave Hydraulic diameter frontalheat expansion modulus/segment sectional component conversion Segmentdiameter HD area conductivity coefficient Young's area diameter Dcomponent length HD/segment (mm) (%) (W/mK) (ppm/K) modulus (cm²) (mm)diameter D L (mm) length L Ex. 1 0.2 80 1 1.2 0.2 9 40 0.75 30 0.0067

TABLE 2 Bonding part Bonding part thermal expansion Bonding part Young'scoefficient/segment heat capacity/ Bonding/ Cell shape/ modulus/segmentthermal expansion segment heat Bonding part monolithic segment shapeYoung's modulus coefficient capacity width (mm) Ex. 1 BondingTriangle/hexagonal 0.2 1.1 0.8 0.5

The following experiments 1 and 2 were conducted using the heat/acousticwave conversion component of this Example 1.

Experiment 1 was as follows. Firstly, the heat/acoustic wave conversioncomponent of Example 1 was assembled in the power generation system 1000of FIG. 1, instead of the heat/acoustic wave conversion component 1.Then, exhaust gas from an automobile at about 500° C. was allowed toflow into the high-temperature side heat exchanger 2, and thetemperature of the exhaust gas flowing out whose temperature fell tosome extent was measured. Based on a temperature change at this time,the amount of heat flowing into this power generation system wascalculated. Due to the flowing-in of this exhaust gas, the end of theheat/acoustic wave conversion component on the side of thehigh-temperature side heat exchanger 2 had a temperature kept about at500° C. Meanwhile, water at 60° C. was allowed to flow into thelow-temperature side heat exchanger 3 so as to let the end of theheat/acoustic wave conversion component on the side of thelow-temperature side heat exchanger 3 keep the temperature at 60° C.Then, measurement was performed using a microphone or the like as theenergy converter of the power generation system 1000 of FIG. 1 as towhat degree of electric power was generated from acoustic waves by athermoacoustic effect due to the temperature difference between the bothends of the heat/acoustic wave conversion component as stated above.Then, a measurement value of the electric power amount was divided bythe energy conversion efficiency (efficiency to convert acoustic-waveenergy into electric power) of the microphone known beforehand, wherebyan estimated value of acoustic-wave energy was obtained. Then, based onthis estimated value of acoustic wave energy and the amount of heatflowing into the power generation system as stated above, energyconversion efficiency from heat to acoustic-wave energy was obtained. Inthis experiment, working fluid in the looped tube 4, the resonant tube 5and the cells causing self-induced oscillations was helium gas at 10atm.

Experiment 2 was as follows. Flowing-in of the exhaust gas as statedabove was performed continuously for 24 hours. After a lapse of 24hours, damage of the heat/acoustic wave conversion component wasobserved using a magnifying glass so as to examine how many small chipsand cracks it had.

Examples 2, 3 and Comparative Examples 1 to 3

Heat/acoustic wave conversion components as Examples 2, 3 andComparative Examples 1 to 3 were manufactured by the same manufacturingmethod as that of the manufacturing method of Example 1 as stated aboveexcept that a die used for extrusion was different, where theseheat/acoustic wave conversion components were different from Example 1only in the values of parameters (hydraulic diameter HD and HD/L)relating to the hydraulic diameter HD of the cells among the fourteentypes of parameters as stated above.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 2, 3 and Comparative Examples 1 to 3.

Examples 4 to 7 and Comparative Examples 4 to 7

Heat/acoustic wave conversion components as Examples 4 to 7 andComparative Examples 4 to 7 were manufactured by the same manufacturingmethod as that of the manufacturing method of Example 1 as stated aboveexcept that a die used for extrusion was different, where theseheat/acoustic wave conversion components were different from Example 1only in the values of the open frontal area of segments among thefourteen types of parameters as stated above.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 4 to 7 and Comparative Examples 4 to 7.

Examples 8 to 11 and Comparative Example 8

Heat/acoustic wave conversion components as Examples 8 to 11 andComparative Example 8 were manufactured by the same manufacturing methodas that of the manufacturing method of Example 1 as stated above exceptthat a ceramic raw material was different, where these heat/acousticwave conversion components were different from Example 1 only in theparameters (heat conductivity and thermal expansion coefficient)relating to heat conductivity of the segments among the fourteen typesof parameters as stated above. For Examples 8 and 9, the ratio of talc,kaolin, alumina and boehmite in Example 1 was changed, whereby theheat/acoustic wave conversion component had heat conductivity higherthan or at the same degree as that of Example 1. For Examples 10, 11 andComparative Example 8, an alumina-cordierite based composite material, ametal silicon-silicon carbide-cordierite based composite material, and asilicon carbide-cordierite based composite material were used,respectively, instead of cordierite forming raw material in Example 1,whereby they had different parameters relating to heat conductivity fromthat of Example 1.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 8 to 11 and Comparative Example 8.

Comparative Example 9

A heat/acoustic wave conversion component as Comparative Example 9 wasmanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that it did notinclude the step to bond a plurality of honeycomb segments, i.e., theheat/acoustic wave conversion component was manufactured including onlyone honeycomb segment, where the heat/acoustic wave conversion componentwas different from Example 1 only in that the segmented structure(bonded type/monolithic type) was of a monolithic type.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for this Comparative Example 9.

Examples 12, 13 and Comparative Examples 10 to 14

Heat/acoustic wave conversion components as Examples 12, 13 andComparative Examples 10 to 14 were manufactured by the samemanufacturing method as that of the manufacturing method of Example 1 asstated above except that the length of extrusion was different duringextrusion, where these heat/acoustic wave conversion components weredifferent from Example 1 only in the values of parameters (length L, L/Dand HD/L of segment) relating to the length L of the segment among thefourteen types of parameters as stated above.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 12, 13 and Comparative Examples 10 to 14.

The following Table 3 shows the experimental results of Examples 1 to 13and Comparative Examples 1 to 14 as explained above, together with thevalues of parameters different from those of Example 1.

TABLE 3 Segment length Segment Segment L/heat/acoustic Cell open Segmentthermal wave Hydraulic Energy hydraulic frontal heat expansionconversion Segment diameter conversion diameter area conductivitycoefficient Bonding/ component length L HD/segment efficiency Damage HD(mm) (%) (W/mK) (ppm/K) monolithic diameter D (mm) length L (%) degreeEx. 1 0.2 80 1 1.2 Bonding 0.75 30 0.0067 30 0 Ex. 2 0.3 80 1 1.2Bonding 0.75 30 0.0100 27 0 Ex. 3 0.4 80 1 1.2 Bonding 0.75 30 0.0133 220 Comp. Ex. 1 0.45 80 1 1.2 Bonding 0.75 30 0.0150 9 0 Comp. Ex. 2 0.680 1 1.2 Bonding 0.75 30 0.0200 5 0 Comp. Ex. 3 1 80 1 1.2 Bonding 0.7530 0.0333 2 0 Comp. Ex. 4 0.3 25 1 1.2 Bonding 0.75 30 0.0100 2 0 Comp.Ex. 5 0.3 35 1 1.2 Bonding 0.75 30 0.0100 5 0 Comp. Ex. 6 0.3 55 1 1.2Bonding 0.75 30 0.0100 9 0 Ex. 4 0.3 60 1 1.2 Bonding 0.75 30 0.0100 200 Ex. 5 0.3 70 1 1.2 Bonding 0.75 30 0.0100 21 0 Ex. 6 0.3 80 1 1.2Bonding 0.75 30 0.0100 22 0 Ex. 7 0.3 93 1 1.2 Bonding 0.75 30 0.0100 220 Comp. Ex. 7 0.3 95 1 1.2 Bonding 0.75 30 0.0100 20 9 Ex. 8 0.3 80 11.2 Bonding 0.75 30 0.0100 28 0 Ex. 9 0.3 80 1.5 1.2 Bonding 0.75 300.0100 25 0 Ex. 10 0.3 80 5 4 Bonding 0.75 30 0.0100 20 2 Ex. 11 0.3 805 4 Bonding 0.75 30 0.0100 20 2 Comp. Ex. 8 0.3 80 7 3 Bonding 0.75 300.0100 5 9 Comp. Ex. 9 0.2 80 1 1.2 Monolithic 0.75 30 0.0067 30 9 Comp.Ex. 10 0.2 80 0.2 1.2 Bonding 0.1  4 0.0500 18 6 Comp. Ex. 11 0.2 80 0.21.2 Bonding 0.25 10 0.0200 19 3 Ex. 12 0.2 80 0.2 1.2 Bonding 0.3 120.0167 30 0 Ex. 13 0.2 80 0.2 1.2 Bonding 0.95 38 0.0053 32 0 Comp. Ex.12 0.2 80 0.2 1.2 Bonding 1.1 44 0.0045 25 3 Comp. Ex. 13 0.2 80 0.2 1.2Bonding 1.5 60 0.0033 23 3 Comp. Ex. 14 0.2 80 0.2 1.2 Bonding 1.6 640.0031 22 9

In Table 3, as is found from a comparison between Examples 1 to 3 andComparative Examples 1 to 3 having mutually different hydraulicdiameters HD of the cells (and ratios HD/L), Examples 1 to 3 had muchhigher energy conversion efficiency than Comparative Examples 1 to 3.This shows that the hydraulic diameter HD of cells of 0.4 mm or less isrequired to exert a large thermoacoustic effect.

In Table 3, as is found from a comparison between Examples 4 to 7 andComparative Examples 4 to 7 having mutually different open frontal areasof cells, Examples 4 to 7 had much higher energy conversion efficiencythan Comparative Examples 4 to 6, and had much less damage thanComparative Example 7. This shows that the open frontal area at each endface of a honeycomb segment that is 60% or more and 93% or less isrequired to have adequate balance between a large thermoacoustic effectachieved and avoidance of damage.

In Table 3, as is found from a comparison between Examples 8 to 11 andComparative Example 8 that were mutually different in heat conductivity(and thermal expansion coefficient), Examples 8 to 11 had much higherenergy conversion efficiency than Comparative Example 8, and had muchless damage than that. This shows that the heat conductivity of thematerial making up the honeycomb segment that is 5 W/mK or less isrequired to have a large thermoacoustic effect and to avoid damage.

In Table 3, as is found from a comparison between the bonded typeExample 1 and Comparative Example 9, Example 1 had much less damage thanComparative Example 9. This shows that the bonded type is required toavoid damage.

In Table 3, as is found from a comparison between Examples 12, 13 andComparative Examples 10 to 14 that were mutually different in ratio HD/L(further L and L/D), Examples 12, 13 had much higher energy conversionefficiency and much less damage than Comparative Examples 10 to 14. Thisshows that the ratio HD/L of 0.005 or more and less than 0.02 isrequired to have a large thermoacoustic effect and to avoid damage.

Herein, in Table 3, focusing on the length L of the honeycomb segmentonly, Comparative Example 10 and Comparative Example 14 had extremelybad results for both of the energy conversion efficiency and damageamong Examples 12, 13 and Comparative Examples 10 to 14. Then, it can besaid that the length L of the honeycomb segment that is about 5 mm ormore and 60 mm or less is desirable.

The following describes other examples.

Examples 14 to 16

Heat/acoustic wave conversion components as Examples 14 to 16 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that adifferent die was used during extrusion, where these heat/acoustic waveconversion components were different from Example 1 in cell shape orhoneycomb segment shape.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 14 to 16.

The following Table 4 shows the results, together with different cellshapes and honeycomb segment shapes from those of Example 1.

TABLE 4 Energy conversion Damage Cell shape/segment shape efficiency (%)degree Ex. 1 Triangle/hexagonal 30 0 Ex. 14 Triangle/triangle 30 1 Ex.15 Quadrangle/quadrangle 28 3 Ex. 16 Hexagonal/hexagonal 24 0

In Table 4, as is found from a comparison between Example 1 and Example14 having the triangular cell shape and the triangular or hexagonalhoneycomb segment shape and Examples 15 and 16 having other cell shapesand honeycomb segment shapes, Example 1 and Example 14 had slightlyhigher energy conversion efficiency than Examples 15 and 16. This showsthat a triangular cell shape and a triangular or hexagonal honeycombsegment are preferable for a large thermoacoustic effect.

Examples 17 to 28

Heat/acoustic wave conversion components as Examples 17 to 28 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that materialsof the circumferential wall and the bonding part were different, wherethese heat/acoustic wave conversion components were different fromExample 1 in any one of the Young's modulus at the circumferential wall,and the Young's modulus, the thermal expansion coefficient, and the heatcapacity per unit volume of the bonding part.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 17 to 28.

The following Table 5 shows the results, together with the value of theparameters different from those of Example 1.

TABLE 5 Bonding part Circumferential wall Bonding part thermal expansionBonding part Energy Young's Young's coefficient/segment heat capacity/conversion modulus/segment modulus/segment thermal expansion segmentheat efficiency Damage Young's modulus Young's modulus coefficientcapacity (%) degree Ex. 17 0.25 0.2 1.1 0.8 30 0 Ex. 18 0.32 0.2 1.1 0.830 2 Ex. 19 0.4 0.2 1.1 0.8 30 3 Ex. 20 0.2 0.28 1.1 0.8 30 0 Ex. 21 0.20.34 1.1 0.8 30 1 Ex. 22 0.2 0.45 1.1 0.8 30 2 Ex. 23 0.2 0.2 0.6 0.8 302 Ex. 24 0.2 0.2 0.7 0.8 30 0 Ex. 25 0.2 0.2 1.2 0.8 30 1 Ex. 26 0.2 0.21.5 0.8 30 2 Ex. 27 0.2 0.2 1.1 0.45 20 2 Ex. 28 0.2 0.2 1.1 0.5 28 2

In Table 5, as is found from a comparison between Examples 17 to 19having mutually different ratios of the Young's modulus at thecircumferential wall to the Young's modulus of the honeycomb segment,Example 17 had slightly less damage than Examples 18 and 19. This showsthat the Young's modulus of the material making up the circumferentialwall being less than 30% of the Young's modulus of the material makingup the honeycomb segment is preferable to avoid damage.

In Table 5, as is found from a comparison between Examples 20 to 22having mutually different ratios of the Young's modulus at the bondingpart to the Young's modulus of the honeycomb segment, Example 20 hadslightly less damage than Examples 21 and 22. This shows that theYoung's modulus of the material making up the bonding part being lessthan 30% of the Young's modulus of the material making up the honeycombsegment is preferable to avoid damage.

In Table 5, as is found from a comparison between Examples 23 to 26having mutually different ratios of the thermal expansion coefficient atthe bonding part to the thermal expansion coefficient of the honeycombsegment, Examples 24, 25 had slightly less damage than Examples 23 and26. This shows that the thermal expansion coefficient of the materialmaking up the bonding part being 70% or more and less than 130% of thethermal expansion coefficient of the material making up the honeycombsegment is preferable to avoid damage.

In Table 5, as is found from a comparison between Examples 27 and 28having mutually different ratios of the heat capacity per unit volume atthe bonding part to the heat capacity per unit volume of the honeycombsegment, Example 28 had higher energy conversion efficiency than Example27. This shows that the heat capacity per unit volume of the materialmaking up the bonding part being 50% or more of the heat capacity perunit volume of the material making up the honeycomb segment ispreferable to have a larger thermoacoustic effect.

Examples 29 to 32

Heat/acoustic wave conversion components as Examples 29 to 32 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that differentdies were used during extrusion, where these heat/acoustic waveconversion components were different from Example 1 only in the value ofcross-sectional area of the honeycomb segment among the fourteen typesof parameters as stated above.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 29 to 32.

Examples 33 to 35

Heat/acoustic wave conversion components as Examples 33 to 35 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that acordierite forming raw material was different, where these heat/acousticwave conversion components were different from Example 1 only in thevalue of thermal expansion coefficient of the honeycomb segments amongthe fourteen types of parameters as stated above. Herein, theheat/acoustic wave conversion components of these Examples 33 to 35 hadlarger thermal expansion coefficients than Example 1 by changing theratio of talc, kaolin, alumina and boehmite in Example 1.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 33 to 35.

The following Table 6 shows the results of Examples 29 to 35, togetherwith the value of the parameters different from those of Example 1.

TABLE 6 Segment Segment thermal Energy cross- expansion conversionsectional coefficient efficiency Damage area (cm²) (ppm/K) (%) degreeEx. 29 2.5 1.2 25 3 Ex. 30 3 1.2 30 0 Ex. 31 12 1.2 30 0 Ex. 32 12.5 1.224 5 Ex. 33 9 3.7 30 0 Ex. 34 9 6 30 2 Ex. 35 9 8 30 6

In Table 6, as is found from a comparison between Examples 29 to 32having different cross-sectional areas of the honeycomb segment,Examples 30 and 31 had slightly higher energy conversion efficiency andslightly less damage than Examples 29 and 32. This shows that thecross-sectional area of one honeycomb segment of 3 cm² or more and 12cm² or less is preferable for a larger thermoacoustic effect andavoidance of damage.

In Table 6, as is found from a comparison between Examples 33 to 35having different thermal expansion coefficients of the honeycombsegment, Examples 33 and 34 had slightly less damage than Example 35.This shows that the thermal expansion ratio of one honeycomb segment of6 ppm/K or less is preferable for avoidance of damage.

Examples 36 to 39

Heat/acoustic wave conversion components as Examples 36 to 39 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that thediameter of the circle-shape was different when the circumferential partof a plurality of honeycomb segments mutually bonded as a whole is cutto be the circular-shape, where these heat/acoustic wave conversioncomponents were different from Example 1 only in the value of parameters(diameter D and L/D of the heat/acoustic wave conversion component)relating to the diameter D of the heat/acoustic wave conversioncomponent among the fourteen types of parameters as stated above.Herein, in a comparison with Example 1, these Examples 36 to 39 had adifferent number of honeycomb segments included in the heat/acousticwave conversion components (the width of the bonding part was the same).

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 36 to 39. In these experiments 1 and 2, apair of heat exchangers close to both ends of the heat/acoustic waveconversion component also were manufactured for each of Examples 36 to39 so that they had diameters in accordance the diameter D of theheat/acoustic wave conversion components, and then experiments 1 and 2were conducted.

Examples 40 to 43

Heat/acoustic wave conversion components as Examples 40 to 43 weremanufactured by the same manufacturing method as that of themanufacturing method of Example 1 as stated above except that the widthof the bonding part was different when a plurality of honeycomb segmentswere bonded, where these heat/acoustic wave conversion components weredifferent from Example 1 only in the value of parameters (width of thebonding part and the diameter D of the heat/acoustic wave conversioncomponents) relating to the width of the bonding part among the fourteentypes of parameters as stated above.

Then, the two experiments 1 and 2 similar to those for Example 1 wereconducted for these Examples 40 to 43.

The following Table 7 shows the results of Examples 36 to 43, togetherwith the value of the parameters different from those of Example 1.

TABLE 7 Heat/acoustic Segment wave length L/heat/ conversion Bondingacoustic wave Energy component part conversion conversion diameter widthcomponent efficiency Damage D (mm) (mm) diameter D (%) degree Ex. 36 280.5 1.07 24 2 Ex. 37 32 0.5 0.94 30 0 Ex. 38 100 0.5 0.3 30 0 Ex. 39 1200.5 0.25 25 5 Ex. 40 40 0.15 0.75 30 3 Ex. 41 40 0.3 0.75 30 0 Ex. 42 413.5 0.73 26 0 Ex. 43 42 5 0.71 25 3

In Table 7, as is found from a comparison between Examples 36 to 39having different diameters D (and L/D) of the heat/acoustic waveconversion components, Examples 37 and 38 had slightly higher energyconversion efficiency and slightly less damage than Examples 36 and 39.This shows that the diameter D of the heat/acoustic wave conversioncomponent of 30 mm or more and 100 mm or less and L/D of 0.3 or more and1.0 or less are preferable for a larger thermoacoustic effect andavoidance of damage.

In Table 7, as is found from a comparison between Examples 40 to 43having different bonding widths, Examples 41 and 42 had slightly lessdamage than Examples 40 and 43. This shows that the bonding widthbetween neighboring honeycomb segments of 0.2 mm or more and 4 mm orless is preferable for avoidance of damage. Herein, when the bondingwidth is actually 0.2 mm or more and 4 mm or less, the ratio of thetotal cross-sectional area of the bonding part to the cross-sectionalarea of the heat/acoustic wave conversion component in the plane(perpendicular plane) perpendicular to the cell penetrating direction isactually 10% or less. That is, it can be said that preferably thebonding width is 0.2 mm or more and 4 mm or less and the ratio of thetotal cross-sectional area of the bonding part to the cross-sectionalarea of the heat/acoustic wave conversion component is 10% or less.

Then, in order to confirm the effect of the two configurations duringextrusion as stated above, the following experiment for extrusion wasconducted for reference experiment.

(1) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the dummy die used had a rib thickness of 0.09 mm.

(2) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the dummy die used had a rib thickness of 0.10 mm.

(3) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the dummy die used had a rib thickness of 0.04 mm.

(4) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the dummy die used had a rib thickness of 0.03 mm.

(5) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the kneaded material used included water at the ratio in thekneaded material that was about 43 parts by mass (error was within ±1part by mass) with reference to 100 parts by mass of the kneadedmaterial solid component.

(6) Extrusion for a heat/acoustic wave conversion component wasattempted by the same manufacturing method as that of Example 1 exceptthat the kneaded material used included water at the ratio in thekneaded material that was about 39 parts by mass (error was within ±1part by mass) with reference to 100 parts by mass of the kneadedmaterial solid component.

As a result, forming was enabled without problems in (1) and (3), but in(2) and (6), clogging of the kneaded material occurred in the holes inthe forming die, and so forming failed. In (4), considerable pressurewas required for extrusion by the dummy die, which showed thepossibility of damage in the die, and so the experiment was stopped. In(5), the formed body obtained by the extrusion was deformed easily dueto the self weight, and a desired shape was not obtained.

Considering these results together with the successful result ofextrusion in Example 1, it can be found that pre-extrusion is preferablyperformed using a dummy die having a rib thickness of 0.04 mm or moreand 0.09 mm or less and the ratio of water in the kneaded material ispreferably 40 to 42 parts by mass with reference to 100 parts by mass ofthe kneaded material solid component.

The present invention is favorably used in a system that effectivelyuses heat from exhaust gas of automobiles or the like to generateelectric power and cold heat.

DESCRIPTION OF REFERENCE NUMERALS

-   1: heat/acoustic wave conversion component-   1 a: interference member-   2, 2′, 2A, 2A′: high-temperature side heat exchanger-   3: low-temperature side heat exchanger-   3A: low-temperature side heat exchanger-   4: looped tube-   4′: looped tube-   5: resonant tube-   5′: transmission tube-   6: energy converter-   7: acoustic-wave generation part-   11: partition wall-   12: bonding part-   12′: bonding part-   13: circumferential wall-   14: cell-   15: honeycomb segment-   15′: honeycomb segment-   20: heat-exchanging honeycomb structure-   20′: heat-exchanging honeycomb structure-   20 a: partition wall-   20 b: circumferential wall-   20 c: slit-   20 d: cell-   20 s: contact face-   21: high-temperature side annular tube-   211: high-temperature side annular tube-   212: high-temperature side annular tube-   2110: in-tube honeycomb structure-   2120: in-tube honeycomb structure-   21 a: inflow port-   21 b: outflow port-   21 c: heat-receiving region-   21 d: heat-resistant metal plate-   21 e: fin-   22, 23: honeycomb structure-   23′: metal mesh member-   22 a: metal outer tube-   23 a: metal mesh outer tube-   23 b: metalized layer-   30: mesh lamination body-   31: low-temperature side annular tube-   31 a: inflow port-   31 b: outflow port-   32: metal member-   301: die-   303: second plate-shaped part-   305: back hole-   305 a, 309 a, 311 a; open end-   306: second bonding face-   307: first plate-shaped part-   307 a: first layer-   307 b: second layer-   307 ba: other face of second layer-   309: slit-   310: first bonding face-   311: hole part-   313: cell block-   401: die-   402: retainer-   403: rear retaining part-   404: honeycomb formed body-   405: gap-   406: inclined face-   407: opposed face-   550: retainer plate configuration-   552: slit-   553: back hole-   554: die-   555: retaining plate-   557: gap part-   558: retaining jig-   559: rear-retaining plate-   561: extruded forming raw material-   571: inside part-   572: circumference part-   573, 574: slit-   575: step height-   602, 702: slit-   603, 703: back hole-   604, 704: die-   605, 705: retaining plate-   615, 715: step height-   100: heat/acoustic wave conversion unit-   200: heat/acoustic wave conversion unit-   100 a: housing-   1000: power generation system-   2000: cold heat generation system

What is claimed is:
 1. A heat/acoustic wave conversion component havinga first end face and a second end face, comprising: a plurality ofmonolithic honeycomb segments each including a partition wall thatdefines a plurality of cells extending from the first end face to thesecond end face, inside of the cells being filled with working fluidthat oscillates to transmit acoustic waves, the plurality of monolithichoneycomb segments each mutually converting heat exchanged between thepartition wall and the working fluid and energy of acoustic wavesresulting from oscillations of the working fluid; a bonding part thatmutually bonds side faces of the plurality of honeycomb segments; and acircumferential wall that surrounds a circumferential face of ahoneycomb structure body made up of the plurality of honeycomb segmentsand the bonding part, wherein hydraulic diameter HD of the heat/acousticwave conversion component is 0.4 mm or less, where the hydraulicdiameter HD is defined as HD=4×S/C, where S denotes an area of across-section of each cell perpendicular to the cell extending directionand C denotes a perimeter of the cross section, an open frontal area ateach end face of the honeycomb segments is 60% or more and 93% or less,heat conductivity of a material making up the honeycomb segments is 5W/mK or less, and let that L denotes a length of each honeycomb segmentfrom the first end face to the second face, a ratio HD/L of thehydraulic diameter HD to the length L of the honeycomb segment is 0.005or more and less than 0.02.
 2. The heat/acoustic wave conversioncomponent according to claim 1, wherein the cells have the cross sectionof a triangular shape, and a cross section of the honeycomb segmentsthat is parallel to the cross section of the cells has a hexagonalshape.
 3. The heat/acoustic wave conversion component according to claim2, wherein Young's modulus of materials making up the bonding part andthe circumferential wall are both less than 30% of Young's modulus of amaterial making up the honeycomb segments, a thermal expansioncoefficient of the material making up the bonding part is 70% or moreand less than 130% of a thermal expansion coefficient of the materialmaking up the honeycomb segments, and heat capacity per unit volume ofthe material making up the bonding part is 50% or more of heat capacityper unit volume of the material making up the honeycomb segments.
 4. Theheat/acoustic wave conversion component according to claim 3, wherein abonding width of two of the honeycomb segments bonded mutually is 0.2 mmor more and 4 mm or less, and in a plane perpendicular to the extendingdirection, a ratio of a total cross-sectional area of the bonding partto a cross-sectional area of the heat/acoustic wave conversion componentis 10% or less.
 5. The heat/acoustic wave conversion component accordingto claim 4, wherein each of the plurality of honeycomb segments has across-sectional area in a plane perpendicular to the extending directionthat is 3 cm2 or more and 12 cm2 or less.
 6. The heat/acoustic waveconversion component according to claim 5, wherein let that D denotes anequivalent circle diameter of a cross section of the heat/acoustic waveconversion component in a plane perpendicular to the extendingdirection, the equivalent circle diameter D is 30 mm or more and 100 mmor less, and a ratio L/D of the length L of the honeycomb segments tothe equivalent circle diameter D is 0.3 or more and 1.0 or less.
 7. Theheat/acoustic wave conversion component according to claim 1, whereinthe cells have the cross section of a triangular shape, and a crosssection of the honeycomb segments that is parallel to the cross sectionof the cells has a triangular shape.
 8. The heat/acoustic waveconversion component according to claim 7, wherein Young's modulus ofmaterials making up the bonding part and the circumferential wall areboth less than 30% of Young's modulus of a material making up thehoneycomb segments, a thermal expansion coefficient of the materialmaking up the bonding part is 70% or more and less than 130% of athermal expansion coefficient of the material making up the honeycombsegments, and heat capacity per unit volume of the material making upthe bonding part is 50% or more of heat capacity per unit volume of thematerial making up the honeycomb segments.
 9. The heat/acoustic waveconversion component according to claim 8, wherein a bonding width oftwo of the honeycomb segments bonded mutually is 0.2 mm or more and 4 mmor less, and in a plane perpendicular to the extending direction, aratio of a total cross-sectional area of the bonding part to across-sectional area of the heat/acoustic wave conversion component is10% or less.
 10. The heat/acoustic wave conversion component accordingto claim 9, wherein each of the plurality of honeycomb segments has across-sectional area in a plane perpendicular to the extending directionthat is 3 cm2 or more and 12 cm2 or less.
 11. The heat/acoustic waveconversion component according to claim 10, wherein let that D denotesan equivalent circle diameter of a cross section of the heat/acousticwave conversion component in a plane perpendicular to the extendingdirection, the equivalent circle diameter D is 30 mm or more and 100 mmor less, and a ratio L/D of the length L of the honeycomb segments tothe equivalent circle diameter D is 0.3 or more and 1.0 or less.
 12. Theheat/acoustic wave conversion component according to claim 1, whereinYoung's modulus of materials making up the bonding part and thecircumferential wall are both less than 30% of Young's modulus of amaterial making up the honeycomb segments, a thermal expansioncoefficient of the material making up the bonding part is 70% or moreand less than 130% of a thermal expansion coefficient of the materialmaking up the honeycomb segments, and heat capacity per unit volume ofthe material making up the bonding part is 50% or more of heat capacityper unit volume of the material making up the honeycomb segments. 13.The heat/acoustic wave conversion component according to claim 1,wherein a bonding width of two of the honeycomb segments bonded mutuallyis 0.2 mm or more and 4 mm or less, and in a plane perpendicular to theextending direction, a ratio of a total cross-sectional area of thebonding part to a cross-sectional area of the heat/acoustic waveconversion component is 10% or less.
 14. The heat/acoustic waveconversion component according to claim 1, wherein each of the pluralityof honeycomb segments has a cross-sectional area in a planeperpendicular to the extending direction that is 3 cm² or more and 12cm² or less.
 15. The heat/acoustic wave conversion component accordingto claim 1, wherein let that D denotes an equivalent circle diameter ofa cross section of the heat/acoustic wave conversion component in aplane perpendicular to the extending direction, the equivalent circlediameter D is 30 mm or more and 100 mm or less, and a ratio L/D of thelength L of the honeycomb segments to the equivalent circle diameter Dis 0.3 or more and 1.0 or less.
 16. The heat/acoustic wave conversioncomponent according to claim 1, wherein the material making up thehoneycomb segments has a ratio of thermal expansion at 20 to 800° C.that is 6 ppm/K or less.
 17. The heat/acoustic wave conversion componentaccording to claim 1, wherein the honeycomb segments have a length Lthat is 5 mm or more and 60 mm or less.
 18. A heat/acoustic waveconversion unit, comprising the heat/acoustic wave conversion componentaccording to claim 1, in a state where inside of the plurality of cellsof the honeycomb segments is filled with the working fluid, when thereis a temperature difference between a first end part on the first endface side and a second end part on the second end face side, thehoneycomb segments oscillating the working fluid along the extendingdirection in accordance with the temperature difference and generatingacoustic waves; and a pair of heat exchangers that are disposed in avicinity of the first end part and the second end part of theheat/acoustic wave conversion component, respectively, the heatexchangers exchanging heat with the both end parts to give a temperaturedifference between the both end parts.
 19. A heat/acoustic waveconversion unit comprising: the heat/acoustic wave conversion componentaccording to claim 1, in a state where inside of the plurality of cellsof the honeycomb segments is filled with the working fluid, and when theworking fluid oscillates along the extending direction while receivingacoustic waves transmitted, the honeycomb segments generating atemperature difference between a first end part on the first end faceside and a second end part on the second end face side in accordancewith oscillations of the working fluid; a heat exchanger that isdisposed in a vicinity of one of the first end part and the second endpart of the heat/acoustic wave conversion component, the heat exchangersupplying heat to the one end part or absorbing heat from the one endpart to keep a temperature at the one end part constant; and a hotheat/cold heat output unit that is disposed in a vicinity of the otherend part of the first end part and the second end part of theheat/acoustic wave conversion component that is on the opposite side ofthe one end part, the hot heat/cold heat output unit outputting hot heator cold heat obtained from exchanging of heat with the other end part sothat, in a state where the temperature of the one end part is keptconstant by the heat exchanger and when the heat/acoustic waveconversion component receives acoustic waves transmitted, the other endpart has a temperature difference in accordance with oscillations of theworking fluid due to transmission of the acoustic waves with referenceto the one end part kept at the constant temperature.